Linux ditributions are the packages you can buy in stores, like:

• Red Hat Linux
• SuSE Linux
• Mandrake Linux
• Corel Linux
• And many many more

There packages give you a easy installation, with or without a helpdesk support, and a lot of additional software to get working with Linux. The additional software can be:

• Office packages (StarOffice, KOffice)
• Image View/Manipulation (GIMP)
• Internet Software (Netscape, Mozilla)
• And many more

The reason why making the correct choice is important: The distribution must contain software you need.
So in our case, we want it to contain HAM software. The only one I know that contains HAM software is SuSE Linux.