Why does bluetooth exist?

Bluetooth technology is useful when transferring information between two or more devices that are near each other when speed is not an issue, such as telephones, printers, modems and headsets. It is best suited to low-bandwidth applications like transfering sound data with telephones (i.e. with a Bluetooth headset) or byte data with hand-held computers (transferring files) or keyboard and mice.

Wi-Fi is better suited for operating full-scale networks because it enables a faster connection, better range from the base station, and better security (if configured properly) than Bluetooth.

Bluetooth is a low power, short range alternative to using cables.

It is not restricted to file transfer, but is often used to wirelessly connect headsets, handsfrees, speakers etc to portable or stationary devices.

It also does not require a WiFi network to be present, and can negotiate directly with other bluetooth capable devices.

Personally I use it with my phone and handsfree.

I have a bluetooth handsfree clipped to my car sunshade. When both by phone BT is active and my handsfree is on, it autoconnects when in range. I can keep my phone in my jacket, and receive and make calls over loudspeaker on my handsfree overhead.

bluetooth is a technology allowing wireless connection between devices. wifi is a technology that allows acces to the internet in a wireless fashion. the difference is whats being connected

Bluetooth connects things wirelessly but without using an Internet connection. WiFi however uses an Internet connection, but that isn't always available.