phonemes?

Hi there, I don't know if anyone out there can help me with this but if someone can I would be very grateful! I'm starting teacher training soon and I've got to do an English test before I start as part of the course. One of the things I need to know about are phonemes; now I've never come across them before so I'm not entirely sure what they are - can anyone help me out?! As part of the question I've got to answer how many phonemes there are in the words 'to', 'wing', 'jumped', 'the' and 'scrunch'. If anyone can explain please do!! :)

[Casiopea]

Try this.

Question: How many sounds do you hear in the word box?
Answer: [a] [k] [s]. There are four sounds in all.

In English the sounds [b] [a] [k] [s] are distinctive (they have different sounds) and they are contrastive, like this,

[b][b]at "bat"
[k]at "cat"
[s]at "sat"

[a]x "ox"
[ae]x "axe"

Change the sound and a new word results. That means, [a] [k] [s] are phonemes in English.

Now let's try another word, say, sing.

Question: How many sounds?
Answer: [s] [I] [ng]. There are three sounds. Note, [ng] represents one sound.

Phoneme test:
sing
sin
cigg "cigarette"


Change the sound and a new word results.

Now try jumped. How many sounds do you hear? (Hint: try not to look at the word. Rely on your ears.)