What are the differences between all the different versions of Windows 7?

Windows 7 Home is divided into Basic and Premium, the differences between the two is Basic is no-frills 7, while Premium comes with Aero Glass. Home is essentially your everyday multimedia design with limited customization beyond how it looks. It’s the most simplified version with less networking, compatibility and flexibility options.
Professional/Business is meant for networking and security, it does have multimedia options and improved capabilities but is also very flexible when it comes to networking options over Home editions.
Ultimate is exactly that, it has everything. Professional has many of the options that Ultimate has, including the ability to run the XP subsystem for compatibility. However Ultimate is by far the most customizable of the three. Professional is the best value, Home Premium is a good choice if you just want the multimedia capabilities and Home Basic is good if you just want the major features without all the jazz of the Premium/Professional, but be prepared for reduced networking and security when using either of the Home editions.
This is a basic overview, for a more complete list of the differences pop on over here.

Oh my god theres different versions of windows 7?

Yes, my computer came with Home Premium, and I was wondering what the other versions do differently.