In simplest terms, a web host is nothing more than a computer that displays your website to the world.  In fact, if setup correctly, the computer you are currently viewing this webpage on could host your website with very little work on your part.  Generally speaking though, you want to leave this to the professionals as they provide a much more stable solution that won't go down when you turn off your computer.  When searching for a hosting provider there are several questions that you need to ask to make sure you are getting exactly what you need at a price you can afford.

Which operating system do I need?:

Most web hosting companies offer a choice between Windows and Linux.  Usually Windows servers are more expensive because the hosting company has to purchase licenses from Microsoft in order to use them.  If you are building a site that uses only HTML files and Images, or PHP, you can stick with a Linux solution.  On the other hand, if you are using software that requires ASP (active server pages) or ASP.NET, then you will have to use a Windows server.  So, in order to answer this question, you need to know what kind of software you plan to run on it.

How much hard drive space do I need?: