ELI5: How did free URL services work back in the day? (randomblog.blogspot.com -> randomblog.com.tt)

This post is gonna date me a little but back in the day, if you had a personal web 1.0. page, you could insert it onto different websites and it would give you a functional domain URL for free. So instead of a blogspot.com domain you'd have .uk.tt or something similar

How did that work? And how do you make momey of off it?