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 [...]

The great thing about computer connections is that they were designed to be “idiot proof” for the most part.  Very few things can be plugged into the wrong place without force, and if it is plugged into the wrong place, usually no damage is done.  All you have to do is match up the shapes [...]