Is teamspeak something web hosting related?
Santrex.net is web hosting provider and they offer that teamspeak
What is teamspeak? Something sorta Voip? or web hosting related? If not web hosting related why web hosting company offer that?

Teamspeak is a voice chat software. It is very common amongst gaming groups for communicating while playing games together (most often a First Person Shooter or MMORPG). Teamspeak uses a centralized server architecture. Many web hosts also offer teamspeak because they high bandwidth, high uptime, static IP based servers already, so offering teamspeak servers is an easy way to make some extra cash. I believe teamspeak servers are completely free to run. You'll also see another program called Ventrilo which is very similar. Teamspeak has a few more features, but Ventrilo has much better sound quality (better codecs). Ventrilo is rather expensive as far as server licenses go. Both of the clients are free downloads.

If they are free you may try them freely.

teamspeak = old and busted

Ventrilo = new hotness.

Most the professional pvp/fps'ers and mmo raiders use it. Teamspeak is of a much lower quality, you wouldn't believe how different voices sound between the two until you try them both.

And yes I made an MIB reference.

Is Teamspeak used to provide Voip service?

You could call it VOIP, because it is voice travelling over IP. However it is not a telephony service in any way, and you have to be connected to the same server at the same time to talk to somebody. It's easiest to think of it like an IRC server, but with Voice. It has seperate channels you can go into, but you still have to be on the same server to talk to somebody.

That is some kind of Voip. I have seen lots of companies offering that nowadays.