Weighted bobber and flies?!

I just got back into fishing (caught my first trout since being a little kid up in Sequoia National Park three days ago). I got the itch again and am planning a little trip to fish a pretty nice river in the next few weeks. I was watching a video of a guy fishing there and he was using a spinner reel (I’m not a fly fisher…yet), with a fly and a weighted bobber. This was all foreign to me because I’ve really only ever just used a weight and some power bait.

Two questions:

What is a weighted bobber exactly (I know what a bobber is but have never heard of a weighted bobber)

And besides using a fly/weighted bobber setup, how else would I fish a pretty good moving river.