Pizzagate is a debunked alt-right conspiracy theory [1]. Epstein ran a child prostitution ring for himself and his inner circle [2]. Pizzagate conspiracy theorists have attempted to graft their theory onto the Epstein case in ways that are largely internally inconsistent. From what I can tell, it's been more successful in tethering itself to the Qanon movement.
There have been many cases of the wealthy and powerful abusing children (Jared Fogle comes to mind,) but to connect it to Pizzagate really commits you to believe some pretty wild things (like the Clintons and celebs like Katy Perry are Satanists who ritualistically abuse children in service to Satan and do so out of a NY pizza joint called Comet Ping-Pong) [3].