USB uses differential signals to transmit data

One to four wires (power, ground, data+, data-),

You say The + and - are data + and data -,

But USB uses a half-duplex communication mode, that is to say, these two lines send signals at the same time, or receive signals at the same time.

The advantage of this is anti-interference (interference can be eliminated through internal circuits, which is the benefit of differential transmission).

The differential voltage of USB is about 2.8V, and different manufacturers produce equipment. There will be some differences, but they will not affect work.