There are several types of hosting:
Not all companies, but some do, fail to mention the 'extras or hidden costs' in their "free website" offers, which are not mentioned until you have actually signed up with them, such as your "free" website comes without it's own domain name (www.yourownwebsite.com) and if you require one, you will have to pay for it and they will probably charge you more than they should.
There may be a stipulation that you display only their advertisements all over the site, which means that they, not you, will earn money from your website.
In order to remove their ads. and replace them with your own, you will probably have to upgrade by buying one of their "premium packages, which contain any good benefits they may be offering anyway.
However, the reason why these "free" web hosts thrust their own advertising onto your website, is to cover the costs they accrue by providing your website with the free space and attendant services in the first place. Therefore, free web hosts which do not impose any advertisements on sites which they host on their server do tend to disappear very rapidly and without warning.
My personal advice to you is to always purchase your own domain name, without exception and if at all possible to use a commercial web host.
It will appear on your page as: