"Musical Instrument Digital Interface" - a method of sending note and tempo data back and forth from hardware or software used to make music.

No, midi sends music information over the midi cable. Information concerning which note you played, for how long, how loud it is played, at which channel, and so on...

So, if your instrument and the computer you're connecting with don't have the same instrument library, the notes, the length, the relative volume and so on will be the same, but it will sound different. Example, you could be playing on a piano, but the sound could be a trumpet.

No.

Line in is for audio, but midi is for midi.

midi = noon, midday

après midi = afternoon

MP3

answer is MIDI