An Erne is an advanced pickleball shot where you hit the ball in the air as you're jumping out of the kitchen zone. After you hit the shot, your feet land out of bounds.
A Bert is the same thing but you have to cross over to your partner's half of the court to execute it. Basically, you jump across your partner's side of the kitchen, hit the ball, and land out of bounds.
These shots are named after the famous partners from Sesame Street, Bert and Ernie. The shot is spelled "Erne", though, because it was created by a player named Erne Perry. This shot inspired the Erne pickleball machine name.