TeamSpeak is a VoIP solution that makes it easy for groups of people to join an online audio conversation with each other thats perfect for in game chat. Some games don’t come with an in game live chat (both text bast and through a microphone) so gamers resort to renting TeamSpeak servers to solve this problem.
To host a TeamSpeak server you need a continuously running machine with a good connection to the internet for everyone to join in. Renting a TeamSpeak server is a cheap way to take away the hosting responsibility from a member of the group as well as ensure a stable connection is constantly established. Usually TeamSpeak servers are in the dollars per month area and very cost effective.