Many people that I know of have heard the song "Do a deer" from The Sound of Music.   Unfortunately, they often think that "Do, re, mi, fa, sol, la, ti, do" are nonsense syllables that were invented for that song.  They are, in fact, the notes of the solfege scale, spelled alternately as solfeggio.  With those eight nonsense syllables, any number of songs can be sung.  I have found solfege to be a great tool in memorizing music, since it lets you identify intervals and the steps of the scale.

Fixed do vs. movable do

As you can see above, do can represent Middle C.  In that school of thought, no matter what key a song is in, C is always the first note of the scale.  This is a technique used widely in Europe.  On the other hand, movable do is less complicated.  In movable do (otherwise known as tonic sol-fa), the first note of the scale is the key in which the song is placed. 

Hand signals

The corresponding hand signals that go with the solfege scale above were, in part, created by Curwen, but their current form was adapted by Hungarian composer and educator Zoltán Kodály (1882-1967).