Activating my iPod touch?

You activate by wifi to Apple servers. You can connect the iPod via USB tio a computer and activate via iTunes. With the iOS 5 and later ( an new 4G or 5G iPod) yo can activate via wifi without a computer. In both cases you follow the on-screen instructions.

Registering is just telling Apple some information about you and giving them the serial number of the iPod.

Apple - Product Registration - Welcome

Activation is manditory but resgistration is optional.

Registering helps if you have to contact Apple about problems.

Activation is more than connecting the iPod to your computer. During activation the iPod/iTunes sends information to Apple and Apple sends some back to activate the iPod. An internet connection is required.