[walternewton]

And just to add, there is nothing inherently special about the key of C - with no sharps or flats to worry about beginners find it a little easier to work with, but all the interval relationships discussed above are exactly the same for all major keys, it's just the note names that are different (it's a good exercise to write out the scales/chords you're learning in all keys, in circle of fifths order - if you do so you'll quickly start seeing the patterns.)