Generally speaking, if you look at the trading page of an exchange for KOI/BTC (or COXE/BTC, however they designate Coinye) you will see a list of buy orders and a list of sell orders.  Both lists will have different values, depending on how much the people placing the orders are prepared to buy or sell for.

If you look at the highest buy price and the lowest sell price you will generally see that there is a difference (usually 1 Satoshi for KOI/BTC).  For example if I look on Crypto Rush at present I see that the highest buy is 4 Satoshi and the lowest sell is 5 Satoshi.

So deals are currently being struck around the 4-5 Satoshi mark.  If you offer to buy at 5 Satoshi you will get your KOI straight away as there are people waiting to sell at that price.  If you offer to buy at 4 Satoshi your order will go into the queue with others waiting to buy at that price.  If someone then offers to sell (sufficient to cover those ahead of you in the queue, plus your requirements) at 4 Satoshi you will get your coins.

The same applies in reverse when selling KOI for BTC.

Hope that's clear.

Nick