What is the difference between negative voltage and positive voltage ? and What is SB voltage ?

Question

For example a computer power supply produces +5 volt and -5 volt and it also prodused +5vSB. How do they differ ?

Answer 1

Voltages are relative. + 5 is 10 more than -5. Some data circuits use + and - 5 volts. SB is standby voltage. It's there when the computer goes into standby, and keeps the memory alive.

Answer 2

With DC, current always runs from negative to positive. Back 50 years ago (when a lot of cars had 6 V batteries!) there were actually some cars that had their positive poles grounded and the negative was the power lead. They would run with a negative voltage.
The reason computer power supplies have positive and negative power supplies is, so they can run off the same ground but with mutually reversed polarities. Has to do with how different types of transistors need to be powered. (PNP and NPN)

Answer 3

+5vSB is the stand-by voltage. This wire is on even when the computer is turned off.

As far as negative and positive, there's no real difference that matters to the computer user / builder.