what is uke? seme? confused af.

I read Naruto since I was 6, and I'm rooting for Naruto and Sasuke. When I was 12, I'm looking for some fanfiction about SasuNaru, and stumbled upon yaoi, lime, lemon, smut for the first time. I only read about SasuNaru tho. My first feeling was ... wtf is this?? I was inexperienced in sex and found anal sex disgusting. I didn't get people could come up with these fantasies. But I stopped reading, bcs I don't like it the fact that ppl make Naruto "uke", and made him girl-like xD I read them for SasuNaru romance.
Then later I was 20 yo (last year), when I found about shounen ai in mangarock. I read Here U Are and 19 Days. And they are soooooo good, I tried to read yaoi then. I forget what was my first yaoi (other than SasuNaru). Then, a couple months ago I found mangago, and here is like heaven for yaoi and shounen ai fans!!!
since then I am addicted to yaoi. no regret tho.