They’re called conventions. I help run several of them.
It’s funny, but when I was in high school, I was force-fed Bradbury’s Dandelion Wine. Now the only thing I knew about Bradbury was that he wrote science fiction. After finishing the book, I said to myself, “If this is science fiction, I don’t want anything to do with it.”
Ironically, I had been reading my dad’s Doc Savage books for a good 7 years by then. He never mentioned they were SF, just that I was welcome to read them if I liked.
I was in my 30s before a friend at work talked me into reading Tolkein. I read the trilogy straight through three times and have been reading both SF and F ever since.
I was in my early 40s when I found out about SFF conventions or cons as we call them. Now I have worked 6 Worldcons and several regional ones.