Apple launched the App Store in 2008, the year after Cydia arrived. The unofficial store allows users who jailbreak their iPhone and iPad to download apps and add features which Apple did not necessarily approve of.
Over time, Apple has made it harder to jailbreak its devices, and Cydia isn’t as prominent or popular as it once was. In 2010, Cydia developer Jay “Saurik” Freeman said that 4.5 million users searched the store for apps.
The lawsuit follows a number of high profile moves against Apple for similar reasons. In August, Epic Games sued Apple on its App Store rules after trying to get around them. A coalition of companies, including Epic and Spotify, has formed to put pressure on Apple and Google by changing their App Store practices. Apple is also under antitrust control of regulators in Europe and United States.