Since this is beeing asked 10 times a day and I'm sometimes beeing called a scammer, let me explain this for non-english users.
Collateral means that if you give me 10 PED ESI, I have to give you ESI worths of PED in return, until I extract.
Let me draw a picture - you put 10 PED ESI in trade window, I put 95 PED in trade window. We trade, I then extract skill and give you back rifle skills in ESI chip and you give me back my 95 PED.
That's what collateral means, you can look it up, it really does mean that!