Speed is the main difference. USB 2.0 ports transfer up to 480 Mbps (Megabits per second), USB 3.0 ports transfer at 10 times faster, 4.8 Gbps (Giga bits per second). You have to have a 3.0 port on your computer and a 3.0 device to get that speed. It is compatible with 2.0 devices but will only transfer at USB 2.0 speeds