Help on Dolby / Speakers

Hi Guys,

I am getting a Gigabyte Z77X-UD3H mobo. It's has 2/5/7.1 HD VIA audio. Im not sure if it has Dolby? I'm getting 5.1 speakers and looking at the Logitech Z506 Speakers. Are these speaker good or troublesome, i've read some issue with the speakers humming.

This is what i think/gathered thus far.
Dolby is required to split audio into 5.1 channels and if you dont have Dolby then you will hear sound from all around (Surround sound) by default.

If you have Dolby then in a game/movie for example, if a helicopter were flying behind you from left to right, you would hear it from the rear speakers moving from the left to the right.

Is Dolby built into hardware or is it software? Does the Z77X-UD3H motherboard have Dolby. Is Dolby the same as DTS?

Please enlighten me on this, thanks