Another dumb question...
Can they fly or swim or something?
Surfing Pikachu is a Pikachu with a surfboard. With this, they are able to wield the move Surf.
Flying Pikachu is a Pikachu with balloons. With them, he is able to wield the move Fly.
Hope I helped!!
Believe it or not, it's real. There is an event pikachu with fly, surf, and a different move. I don't know when the event was started, but I'm pretty sure it's over now. Hopefully this answers your question. Hope I helped!(ish)