I found a USB cable with three male connectors from somewhere. I'm sorry I don't know what it's called. I've never seen any such cable before. Tried searching on the Internet and many people, couldn't find any answers.
What may be the possible use(s) of this?
A picture of the cable:
One end goes into a external HDD. The other two ends to into a PC. One cable is data, the second also provides additional current for a device that needs more.
Strictly speaking you should never see a type A connector on a device side, and newer versions of USB probably would never have that. Such connectors are USB 2.0 or less usually.
When I've seen this type of configuration, one of the connectors is for data transfer and the other is for providing extra electricity to the USB device. Usually the end that only has one connector will be USB-B.
I've seen a few cables like those and they are usually for external hard drives or other devices that require more power than just one connector can support.
Example hard drive connector:
