To write music, you need a staff, where the most important thing is the clef, which means the key. There are different clefs for different instruments or for singing, but the most important one is the Treble Clef or the G clef. Without clefs, you can't read music, because the notes are dancing freely and ... without any sense, though they may be beautiful as a decoration sometimes.
Look at the picture. Two little children are singing THE WORLD'S MOST BEAUTIFUL SONGS from this pretty book. They can't read nor write, but they like to sing with their mother in the garden, where they take a siesta. Their mother is a concert pianist, and her name is Clara. Their father is Robert Schumann, a composer, and right now he is writing this music which he was playing this evening...
