Order books, matching exact price or closest price? After reading this How do buy and sell orders work?.

This says that closest price, so if someone is selling at 999, and someone offers a bid of 1000, that the 999 will get sold since its the two orders that match closest.

I trade on btce, my understanding was that orders have to match exactly in price. And I take it its considered a sell or buy depending on who goes first.
I haven't really looked at BTCE, yet, but for example on Bitcoin.de also, orders and offers have to match exactly. However, Bitcoin.de is not a real exchange, but more of an auctioning platform/escrow service: Money flows directly through wire transfer from buyer to seller, bitcoins are held by the platform and released as soon as the money transfer was confirmed by the seller.

On Exchanges though, the platform holds both money deposits and bitcoin deposits of the users. The situation there is slightly different: Let me illustrate with a real-life example:

Okay, imagine you want to buy a beard trimmer, because your old one broke. Before you leave the house you decide that you can afford to pay up to 40 € for one. When you get to the electronics store you find the beard trimmer you want for 35 €.

I'll go out on a limb here, but I imagine that you would not go to other stores trying to find it for 40 € because you decided that you wanted to pay that at most.

On the other hand, let's say when you get to the store, the beard trimmer's price is 45 €. There is three options then: Either wait until the price drops to 40 €, look at other stores, or pay more.

Exchanges work the same way:

When your order is higher than the current lowest offer, lucky you, you saved money compared to what you were ready to pay. Yet, when your order is lower than the current lowest offer. You'll have to wait for it to be fulfilled or take your business somewhere else.