In this chapter we'll go through some general stuff concerning MIDI tracks and you can find some more detailed info at this link MIDI@Wikipedia, and also you can read a bit about this GM Map@Wikipedia.
So, in simple language, MIDI is electronic data which we use to tell computer what notes to play, how loud to play, etc. Since it only requires a computer to work with, it's a real treasure for composers and musicians who need to write arrangements and want to do it alone, at home or in the studio.
To expand your sound possibilities it's great to buy some VST instruments from companies like Steinberg, Spectrasonics, Native Instruments or IK Multimedia. There are a lot of companies creating sound samples or VST instruments so with a bit of browsing the internet you'll be able to find a lot of those. often these samples are pricey but i can say that samples from the companies listed above are really worth the price.
If you want to go at low prices, there are always some free VST samples of lower quality but are good for learning and getting into the whole music production thing.
In the lesson you can hear me mentioning some "maps". If you check those Wiki links above i'm sure you'll get even better technical explanation than I can give but usually we only use maps for drums because the editor view is totally different than a "no-drum-map" view. Map is actually something like real map for finding a way between the note you played on MIDI keyboard and the note reproduced by computer. In our case we won't use MIDI keyboard so you don't have to worry about that. However, after we cover some important areas of Cubase I will sure make a lesson on MIDI keyboard connection and setup.
If you're done with this lesson we can move to the next video and see the process of creation of MIDI track and how to work with MIDI tracks and VST instruments.