A single tail, attached to the stem, indicates a quaver while a double-tail ... are simply fractions or divisions. Hence a minim is a half note, crotchet a quarter note, and so on.
Clogs: Yes. They are called semibreve, minim, crotchet and quaver. Naomi: Well, it sounds a bit like you're talking in a different language. Clogs: I am not although I can explain further in a ...