Oops Jim,
My advice is to play around with the keyboard first. One step at the time as a wise person said. If you don't know what midi is than PSRUTI is not going to do much good yet. But keep it for later!
In general: Any keyboard or synthesizer is a midi-instrument and MIDI is a sort of standard computer language telling the soundprocessor inside the kboard what sort of action is going on. The key that is pressed, how hard or soft, how long or short and what sort of voice (piano, violin, saxophone and so on) is used and the sort of accompaniment that is activated.
This all comes out the speakers as music but midi as such is NOT music.
If a keyboard is able to record you performence, it will record it as MIDI thus a long stream of info. And when you download a midi from internet or from another keyboard and are able to put it in your keyboard and play it, the keyboard will translate this midi-info-language into the music you hear.
Now it is time for my lunch.
Come back with questions, we all had to start one day.
DickR