"Everything is an adapter." That is how I explained electronics to my wife, who after that "Aha!" moment, was able to expertly help organize my parts.

Examples:

keyboard - finger input to IBMPC, PS/2, USB, Bluetooth

IBMPC to USB (to plug your beloved IBM full travel keyboard into USB)

A/C outlet to power supply input

A/C input to USB 5 or 20 v output

MIDI to USB

5mm audio to USB

12V to laptop DC

etc, etc