Here you can learn how to read music.
Free music theory lessons online.

This site is for UK music terms.
If you want to learn American (US) music terms, then go to:
http://www.music4musicians.com/minute_a_day_music_theory.htm

Notes that are twice as slow as crotchets are called minims.

Here are two minims.

Here are 2 bars of minims.

Click the play arrow twice.

Now listen to the difference between these three kinds of notes - minims, quavers, crotchets.

Click the play arrow twice.

2 measures 4/4
Click the play arrow twice.