What type of "latch" system does the MacBook use?

The short and direct answer to this question is simply "magnetic". The MacBook uses a magnetic "latch", but it is quite a bit different than the also magnetic latch used on previously released Apple notebook systems.

In Apple's marketing copy for the system, the company said:

Opening and closing your MacBook is a snap, thanks to a magnetic latch that catches without a catch. That means no moving parts to snag, jam, or break.

Photo Credit: Apple Computer (Latch Inset)

Many PowerBook, iBook, and MacBook Pro models have a small "hook" (or two) that are magnetically attracted to a "post". To disengage the latch on these systems, you must push a small button. The MacBook, on the other hand, is "sealed" only with magnets, and must be opened by gently pulling up on the display.

In a great in-depth review that should be read in its entirety, ArsTechnica explains that:

In the lid of the machine, there are two metal plates on each end (use your MagSafe connector to verify). When the lid is closed, these attract to what I presume are magnets in the frame and the machine is held very securely shut. It makes for a very slick looking form factor, and the lack of latches and keyholes really tightens up the already sleek design.

It's a simple and elegant design. Only time will tell if it proves to be more durable than the design used in previous models.