Your hosting account is situated on a server with other customers and is subject to some limitations in regards to server resource usage (you can read more about these limits under 'Advanced Features'). You are given a single cPanel login and using this can fully manage every aspect of your hosting account. This is ideal for a basic hosting account or someone who just needs hosting for a small number of websites.
Reseller hosting gives you the same as shared hosting, except that now you have the ability to create additional accounts with their own unique cPanel login details, completely separate from your own account. This is ideal when you may wish to sell hosting to your clients or others.
This is super-charged Shared Hosting! You get a Shared Hosting account (as above) but with less limitations and higher performance. This is ideal for busier websites that have a lot of concurrent users or need more bandwidth than our shared hosting.
VPS's act like blank servers, but share resources on a hardware node much like shared hosting. VPS's can be used to install your own software, your own operating system and provide you with full control over every aspect of your server. These are ideal for power users, or users who want to install their own server software.