Plenty of info on seasoning in the thread above. So, I won't add to that, but will add a personal anecdote.
50 years ago (exactly, I think) I rented my first apartment and needed some cooking utensils. In my parents' basement, hanging on a nail in the floor joists, was an old cast iron skillet. I asked my mother if I could have it. She said "sure, I haven't used it for years; it's too heavy for me." I asked her how old it was. She said she didn't know; it was old already when her mother gave it to her when she and my father married and set up housekeeping together in ca. 1933! I'm sure it is well over 100 years old and cooked perfect bacon fried rice for breakfast just this morning.