Limit orders

Embarassing question: I’m currently on reading 45 in SS 16. I understand, and have placed, many market and limit orders, but I don’t know exactly what happens between the time I place a limit order and the time I have the securities. Jan 10 XOM 70 calls have a bid of $6.5 and an ask of $6.8. If I place a limit Buy order at Scottrade at $6.6 and the price moves (or someone just decides to sell to me at $6.6) the trade executes and I own the contracts, but what exactly is happening here? Is this automated or is there a specialist looking at my bid? Why is it that if check ‘All or None’ I can’t see my $6.6 bid, but if I leave it unchecked I can see it"? If someone could walk me through how the actual trade occurs on the exchange I would appreciate it.