A host is like an apartment building. Your website is one of the apartments in the building. Hence you pay rent to the apartment building.
Also, a host is like the host or hostess of a party. They provide the food, accommodations and all the right food to make your event a success. When you have any questions you always ask the host. The same is true with the host for your website. It should provide the services you need and quick, speedy access to help when you need it.
If you want information on some decent hosts that we use check out the Resource page.
A host is really a service that gives you space on the internet for your website to live.