What does bluetooth do on the iPhone 4s?

So I just bought the iPhone 4s last Wednesday and 1 thing I've noticed is how quickly the battery drains. I've heard one way (and really the only practical one for me) is turning off bluetooth, but I was wondering if I use it for anything and just don't know? I know it's obviously used for headsets and in cars, but does bluetooth do anything else, regarding network data, etc?

What are some other tips you could suggest for saving battery? I find myself having to charge it nightly.

Really it just cnnects your device to other devices its relativley useless unless you do want to connect it also COMPLETELY closing apps after using them (double press the middle button and a bottom taskbar thing ill pop up with you recently used apps just press and hold them then click the delete X's on them) this should save the battery a bit also turning off 3G and Data saves a bit of battery it can be found in the Settings>General>Networking area.
Hope it helps