Go! Animate is a site, where one can make one's own animations easily.
Go! Animate's animation maker, it allows many features, such as allowing you to choose a character to use, the voice for that character, the background, props and vice versa. If you have a Go! Plus, you could get some more features, however, Go! Plus was removed later on, but something similar still remains.
Popularity of Go! Animate
While Go! Animate did get popular, there are many things that Go! Animate did get famous for, such as the infamous "Grounded Videos", where a character does something that results in them getting grounded for an absurd amount of time (i.e. 49539573947483748364 years), most grounded videos got criticized for how some users punished another user in a grounded video for something they thought was wrong (such as grounded for Making fake VHS openings).