How do you meet fellow ravers?

App to meet other ravers?? You can join one of the serval raving, genre, or artist themed discords (heres /r/avess). They usually have meet ups at larger events.

Whats the difference between a festival and a rave?

Raves, by definition, are large dance parties featuring either DJs or live performers that play electronic dance music or EDM. Whereas, music festivals are simply community events, which feature live musical performances that are often presented with a theme.