There are three types of USB port dictated by the actual current specs (milliamps or mA)
Answered by Rupert, Electrical Safety Expert
There are three types of USB port dictated by the actual current specs (milliamps or mA).
Dedicated charging port.
A dedicated charging port applies to power sources like wall chargers that do not enumerate, so charging occurs with no digital communication at all.
Downstream port.
A charging downstream port can be found on a computer or laptop and can supply up to 1.5A, whilst allowing a USB to be detected and begin charging before enumeration (which is when the digital communication takes place).
Standard downstream port.
A standard downstream port can be found on a computer or laptop and needs to enumerate (start digital communication) to be USB compliant, however most present-day hardware does draw power without enumerating.