Skyrim is a wonderful game, but it's not without bugs and general irritations. Basic mods are aimed at people who just want to get started with modding and make the game work a little better for them. Advanced mods are aimed at people who want to fix more of the annoyances and also add some extra niceness to their experience.
There could be many more mods listed here, but I will leave it up to you to explore the possibilities. The listed mods are the ones that I have personally tested and actually use while playing offline, and while I'm streaming.