Back in 2010, the only definition of fancam on Urban Dictionary was "footage of a celebrity taken by a fan. Most likely to be of low quality." You could find videos on YouTube that fit that definition fairly easily. Virtually any video taken at a concert fit the bill. 

But, even by 2010, the definition was starting to change. The earliest mentions of fancams on Twitter came back in 2008, but, in 2009, the mentions started evolving, focusing mainly on videos of K-pop stars. 

By 2019, there were thousands of fancams of K-pop celebrities on the social media site and they were used in a different way than simply just posting tweets about them. They were used as replies on Twitter threads, usually to up the views of their video but also to spread their favorite stars. The original tweet they were replying to usually has nothing to do with K-pop.