Here is a diagram of some of the typical sound card input and output connections on a computer.
There are normally at least 3 jacks (holes) and a rectangular connector in the sound card section of your computer. The audio output jack, the microphone input jack, the line input jack, and the game port. The 3 similar jacks accept a 1/8″ or 3.5mm (same size) plug. Of course, higher end cards may have more of these types of jacks for extra surround sound speakers, but I am only going to cover the basic type here. The rectangular connector is a 15 pin D-sub connector that’s called the game port.
Audio Output Jack:
The audio output jack is normally color coded green, and is a stereo output for your speakers or headphones.
DO NOT plug your electric guitar amplifier speaker OUTPUT into this jack, or you may have to go shoppin’. You can, however, plug a cord from this audio output jack into your guitar amplifier INPUT to greatly amplify the song playing on your computer. Doing that will also greatly amplify your parent’s/wife’s voice. ;>)
The microphone jack is usually color coded pink and is strictly a low level, mono, microphone input.
Line Input Jack:
The line input jack is usually color coded blue and is for playing or recording music or sounds into your computer from the line output jacks on a keyboard, CD player, etc.
The game port is a 15 pin, D-Sub, input/output (I/O) port for a joystick, game controller, or MIDI device. It’s unique shape and size prevents someone from inserting the connector in wrong, or from inserting the wrong connector in. Here is a diagram of the computer game port pin out:
For older computers that don’t have the MIDI capabilities, pin 12 would be connected to ground and pin 15 would be +5V out.