Can someone describe the Rachel and Finn relationship on Glee?

I just started watching and I love it and I love Rachel and Finn. Theres all the weirdness between them and Quinn. I know they dated but thats all I know. Then today I find out that there was a guy named Jesse that like Rachel. Who is he. What has happened through the seasons with Finn and Rachel? Also if anyone knows where I can watch all episodes from both seasons of glee then please include a link! Thanks!