In recent months the situation of claims and counter-claims with regard to Russian doping at the 2014 Sochi Olympics has become more confusing than ever, with a barrage of acronyms -- IOC, WADA, CAS -- and scores of athletes involved in a spiral of accusations, bans and appeals that are continuing even as the Pyeongchang Games get under way.

Below is an explanation of the key players and issues in the Russian doping saga.

What is the IOC?

The International Olympic Committee is the global body in charge of the Summer and Winter Olympics. It has some 100 members who are elected by their peers. The IOC is funded through broadcast rights deals, sponsorship as well as licensing and marketing.

It says it redistributes 92 percent of its revenues to its stakeholders which are the athletes, the international federations, national Olympic committees and the hosts of the Olympic Games.

What is CAS?

CAS is the Court of Arbitration for Sport, the highest tribunal for the resolution of sports-related disputes. It was set up by the IOC in 1984 to offer resolution of sports-related disputes with the use of arbitrators.

While it says it is independent, senior International Olympic Committee (IOC) member John Coates, heads the International Council of Arbitration for Sport, (ICAS) a body set up to ensure CAS's independence and which is responsible for the administration and financing of CAS.

What is WADA?

The World Anti-Doping Agency, set up by the IOC in 1999, is the global body that drafts and monitors the WADA Code, the document harmonising anti-doping policies in all sports and all countries.

WADA is funded equally by the IOC and governments. Its key activities also include scientific research, education and development of anti-doping capacities. Its annual budget is $30 million a year with WADA wanting to hike it to 45 million, saying the organisation is underfunded.

Why did the Russian athletes appeal to CAS?

The IOC has banned dozens of Russian athletes for doping rule violations during the Sochi Olympics, based on evidence from several investigations. Russia had finished top of the medals table at their home Games. It also banned them for life from the Olympics.

But CAS upheld the appeal for 28 of them citing insufficient evidence. For 11 others evidence was enough to establish anti-doping rule violations but their lifetime Olympic ban was also commuted into a ban just from the Pyeongchang Games.

More Russian athletes have appealed to CAS after they were excluded from the Games despite having no doping sanction. The IOC said they were banned because of evidence and suspicion of wrong-doing.

Who has the ultimate say on whether an athlete can participate in the Olympics?

The IOC reserves the right to include or exclude athletes from the Games. The IOC cannot sanction athletes for any anti-doping rule violation but it can refuse to invite them to its events as it has done with the Russian athletes despite them having been cleared by CAS.

Why did the IOC criticise CAS?

The IOC was stunned when CAS upheld the Russians' appeal, calling the decision surprising and disappointing and one which would have a negative impact on the fight against doping.

While it has always insisted that CAS is the highest sports court IOC President Thomas Bach said change was necessary within CAS to allow it to "better manage the quality and the consistency of its jurisdiction".

Why was Russia investigated in the first place?

Three years ago several media organisations carried claims of extensive doping among Russian athletes at past summer and winter Olympics, but on a huge scale at Sochi.

Federations, the IOC and the WADA launched a string of investigations to look into the issue which ballooned into the biggest doping scandal in years, engulfing many sports and said to involve more than 1,000 athletes.

The IOC has called it an "unprecedented systematic manipulation" of the anti-doping rules and system in Russia.

What were the investigations?

WADA commissioned an independent investigation led by Canadian lawyer Richard McLaren. The IOC then launched two investigations. The first, the Oswald commission, looked into evidence of systematic manipulation of doping samples at the Sochi Games. The second, the Schmid commission, investigated the level of knowledge and possible involvement by the Russian state.

What did they find?

The Oswald commission found that dozens of Russian athletes were involved in anti-doping rule violations at Sochi, widening the Russian doping scandal that had been triggered by track and field athlete-turned-whistleblower Yulia Stepanova.

The Schmidt commission confirmed that the Russian authorities developed a system that allowed a Moscow laboratory to routinely change positive test results to negative, as well as to tamper with samples at Sochi.

What happened then?

In December the IOC banned Russia from competing as an independent nation in Pyeongchang.

It instead carefully screened Russian athletes, and those who had no doping past, had been tested rigorously and were not mentioned in the various reports, were invited to compete in South Korea.

A total of 169 Russians were invited to the Games - the third biggest team after the United States and Canada - and they will compete as "athletes of Russia" under the Olympic flag and not their own.

Who is Grigory Rodchenkov?

Rodchenkov was the head of the Russia's anti-doping laboratory and a key player in Russian doping at Sochi. He made headlines in 2016 as a whistleblower, helping expose the extraordinarily complex and extensive nature of Russia's doping program.

His revelations were confirmed by the McLaren Report, leading to Russia's partial ban from the 2016 Summer Olympics and total ban as an independent nation from the 2018 Winter Olympics.

He is currently living in hiding in the United States.

So why are the Russians appealing?

Those appealing are Russian athletes who have never tested positive or been guilty of a doping rule violation but were still banned from competing in Pyeongchang due to undisclosed evidence or suspicion of wrong-doing.

Of a first batch of appeals, 28 of them had their IOC sanctions and Olympic lifetime bans overturned by CAS, who said that though there might be circumstantial evidence that satisfied WADA and the IOC, it was not enough legally to uphold individual bans.

The IOC has refused to invite them to South Korea saying there was enough evidence in the reports to merit their exclusion, but they are appealing again against that exclusion.

What are the Olympic Athletes from Russian allowed to do in Pyeongchang?

According to the IOC's 'Conduct Guidelines for Olympic Athlete from Russia", athletes must wear only the authorized OAR uniforms and refrain from any public form of publicity associated with the Russian flag, anthem, emblem and symbols.

The Russian national anthem will not be played if they top the podium. Instead it will be the Olympic anthem. The athletes will also march under the Olympic flag at the opening ceremony.

The suspended Russian Olympic Committee will also be responsible for their fans’ behaviour inside the venues and any display of national flags or emblems even at non-official venues must have IOC approval.

If the IOC is satisfied at the end of the games that Russia has stuck to the conduction guidelines then the nation can march in the closing ceremony under its own flag.