Question: what is a 2a usb charger?
Answer: If you are talking about a USB charger, 1A is enough to charge most devices such as GoPros and Bluetooth headsets and phones, but tablets need 2A. (1A means 1 amp - a measure of electrical current - as others said. In the context of a charger, it means "twice as much" or "twice as fast", if the device can use it)