Haha, it's okay! Tumblr was really confusing when I first started, too. Basically, Tumblr is whatever you want it to be. There's a lot of pictures and GIFs, yes, but you can post really long text posts, songs, chats, or anything else you want. What Tumblr is all depends on who you follow. For me, my Tumblr dashboard ends up being a lot of funny jokes with intelligent conversation and stuff pertaining to different things I like.
Anyway, how's your day/evening/time of day going? :p