the icemat siberia do look good, the only thing that puts me off is the detached mic, I'd much rather have an integrated mic on a boom.
XFX headset review
To answer some of the OP questions:
What is a headset used for in gaming:
1) Enables you to clearly hear whats going on with minimum interference from environmental noise.
2) Helps you pinpoint where sounds are coming from and how far away they are, very useful in FPS (shooting) games.
3) A gaming headset includes a microphone for in game communication, be it just chat or team coordination.
Can a gaming headset be used for phone calls on the computer or for typing programs that recognize your voice?
Yes in a word.