What is P(5)?

Answer 1

If you're talking about the power connectors inside of the computer, then you're probably referring to the connector commonly known as a 'Molex' connector. This is actually a P5 connector. It's a 4-pin connector where the pins are about 2mm thick and placed side-by side in a white semitransparent housing like this | o o o o | . P5 connectors provide both +5v and +3.3v as well as have 2 ground wires, they were used to power desktop hard drives and CD/DVD drives before they were replaced by SATA power connectors, though many power supplies made today still come with P5 connectors which are still often used to provide power to case fans and miscellaneous peripherals.

Answer 2

What is P(5)?

Euphemistic reference, not to the statistical "p-value" (at least, not directly related), but to social intercourse where a man is accused of "thinking with his p----." P(5), pronounced "p five", extends the allusion to both men and women, referring to their similar "brains" (two different words with 5 letters each) in the same geographic location.

"P(7)" is a man's mildly incensed retort, meaning "I am and it's 7 - not 5", sometimes nurturing more desirable probability.