Hey,
I don't know Logic that well, but I'm sure that the fundamentals of it are similar to Cubase.
1. It does two things: audio and MIDI.
2. You have a main arrange screen, this is where you lay out your audio and MIDI tracks.
3. There is a mixer which you use to balance the volumes and pans of your audio and MIDI tracks.
4. There are effects which you can run your audio through, like chorus and reverb.
5. The newer versions of Logic come with software synthesizers, these are sort of a weird combination of audio and MIDI: you play them with your MIDI keyboard, but can route them through the audio mixer.
6. It is not a program you learn in a few days. You will pull your hair out trying to figure out how to work everything. It's probably not the best program for a beginner...there are lots of books out there, plus the manual, which should be able to walk you through a few simple processes.
Take care,
Nick