Hi TIMWAR,

I was about to write to Wayne on this, but you bring up the main point.

Some of this may just be terminology among platforms.

I get 4 pieces of data associated with a product on this on my data stream.

Bid, Ask, Bid size, Ask size

I think my Bid, Ask may be what you are calling:
"buy limits below the market and the sell limits above the market"

Often called the bid/ask spread and the current market price is in between.

In general, you can "offer to sell at the Bid and get a fill", or conversely "offer to buy at the Ask and get a fill" -- but not always.

If the volume of trading is light relative to the size of the BidSize/AskSize queue you may/will not get a fill and the market may move away from you.

In which case you should see all four prices change as well.

[Note: This assumes you are not talking about placing a "market order" in which case you should always get a fill, whether happy with it or not !!!]

My understanding/view is that the 4 numbers represent the "current state" of the market, and it will change. The spread (difference between Bid and Ask may widen, or shrink to as little as 1 tick).

The spread and its variation is another discussion.

On This:
"You can't see the buy stops above or the sell stops below."
I think this is only available for a fee, and what is called
"NASDAQ LEVEL II " (you would have to look into this)

I have experimented with this as follows:
As the Bid/Ask moves up/down I have noted the queue sizes at each price, so in that way you can get a peek at what is coming at the next price level .... But I don't know that it is worth the effort beyond getting a handle on what is going on.

I have fiddled with this as follows:
Say I want to sell to close a position and my limit order has not yet filled. I have watched the BidSize tick down and when it gets near where I placed the order, sure enough I got a fill !!! (Note: my offer to sell was at the Bid price, but market volume was not sufficient to get an immediate fill.)

Anyway, hope this answers some of your question. Not something I would want to really have to pay attention to while trading, just some experimenting way back to get a better understanding of what was going on.

Good Luck,
Lee