Compare it to a simple transaction such as the sale of a car.
If you are buying a car, you BID how much you are willing to spend.
If you are selling a car, you ASK for a certain amount.
Naturally, the bid will be lower than the ask because the buyer wants the car cheap, and the seller want as much as he can get for the car.
The seller will sell the car to you only if you pay how much he is asking, right? When a sale occurs, a trade is made. The amount of the transaction is posted, this posting is what you refer to as a quote.
Here may be where you are getting tripped up. The quote is simply the last transaction. It does not say what the next transaction will be. There may be more cars available at that price and there may not be. Could be that the car is no longer available, its gone, someone sold it and someone bought it.
If you really want a car, you will raise your bid to the ask price, and you will buy it. (Called a buy because you came up to the ask price).
If the seller really wants to dump the car, he will lower his price to the bid, and he will sell it (called a sell because he came down to the bid price).
So... you had a sell limit order, the ticker hit your sell limit, but you did not get filled. This is because there were orders ahead of you, and by time they got to your order, no one was willing to buy at your price anymore. This happens often is a low volume market called ('thinly traded'). It is one of many reasons to keep an eye on volume. In a high volume market, you will likely get filled at or very near your number.
L2 (Level 2) Quotes will give you an idea of how many people are lined up to buy and sell at differant prices, but I feel like I just wrote a book - so I'm done. Hope that helped you!
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