What do u guys generally talk about with friends?

I 22M still in clg. My entire school life I never dated nor had any friends. Now i m in clg and regularly see people text or call with their friends. I had a terrible past which took me through depression and even almost suicidal. Thats not the point. The thing is I dont really know how/what to talk to people. I dont know what to talk about and on why people generally laugh while texting with their friends.