What is web hosting?  Put simply web hosting is the computer system that will run your web site.  This system is permanently connected to the internet and plays host to your web site.  When someone tries to connect to your web site it will be your web host that will reply back and send them your site data.  Hosting is an often overlooked part of a web site, but it is vitally important if your site is to provide a fast, responsive experience for your customers.  If a site is slow and keeps disconnecting then nobody will stay on your site for long.  Also the main search engines take into account the response times of site when ranking.  This means a slow site will have less chance of making it to the top of google.