• Storage, the amount of data you can store on your web server
• Monthly Bandwidth, the amount of data you can send and recieve from your web server

However, all of the packages offer a lot of great features :

• cPanel. A very powerful and easy to use browser based site configuration and management software application.
• Unlimited Domain Names and Subdomains
• Unlimited mySQL databases.
• Unlimited FTP Accounts
• Unlimited E-mail Accounts and Mailing Lists
• PHP 5.x, Ruby on Rails, Perl, Cgi-Bin
• No Setup Fee
• And much more!