Types of USB Hubs
Active USB hub and passive USB hub
Active USB hub
Powered or powered USB hubs use an external power source to increase the energy level of each hub port to the energy level of the ports on the system. Powered USB hubs are usually powered from a wall outlet. While an active USB hub is not required to distribute power to all connected devices, the hub does distribute data bandwidth to all connected devices.
In short, a USB port on a computer generates a small amount of electricity. When you "split" a port (by plugging into a hub), power is also distributed among the other ports. And, depending on what devices you plug into the hub, there may not be enough power to handle everything. That's why it's crucial to choose a powered hub that comes with its own AC adapter. You can fill each port with power-hungry devices without worrying about limited amplifiers causing operational problems.
Unpowered USB hub
An unpowered USB hub lacks an external power source and relies solely on the computer's USB port for power. Unpowered hubs have compatibility issues with devices that require more power than the hub can supply.
For example, a USB flash drive may work fine when connected to a computer's USB port or an active hub, but may not power on when connected to a passive hub. The USB 3.0 standard improves on the power management features of previous versions and may be able to use higher power devices that were not available to hubs running the older standard.