Free website hosts often make money in other ways, such as putting banners, popups, or popunders ads on your free webpages. Some free web hosting companies do not put ads on your site, but require you as the webmaster to click on banners in their control panel or signup process, or just display banners in the file manager in hopes you will click them.
Some lure visitors with free hosting in hopes you will upgrade and pay for advanced features. A few send you occasional emails with ads, or may even sell your email address. A new method that is becoming popular is requiring a certain number of "quality" forum posting, usually as a means of getting free content for them and thereby being able to display more ads to their website visitors.
Are free web hosts reliable?