Teamspeak type:
Contract: Regular contract you need to cancel at some point, with monthly recurring fees.
Pay as you go: Daily recurring fees, top up any amount any time

Slots:
Maximum amount of concurrent users

File transfer:
Teamspeak servers may provide file space for up and downloading. Choose the data rate limits for file transfers

File storage:
Teamspeak servers may provide file space for up and downloading. Choose the total amount of file space to provide