What are the differences between a slot and a slat?
I guess it should be movable slat.

A leading edge slot is basically a spanwise opening in the wing. Slats are aerodynamic surfaces in the leading edge, which when deployed, allows the wing to operate at higher angle of attack. When deployed, the slat opens up a slot between itself and the wing.



Image from simhq.com

In some aircraft, the slats are fixed, which opens up a slot between the wing and the slat. In this case, the terms slot and slat are used interchangeably.



"Leading edge slot" by Sanchom - Own work. Licensed under CC BY 3.0 via Commons.

A number of airliners use movable slats, in which case, the system is called slat, rather than slot.



"Voilure A319" by Nicourse - Own work. Licensed under CC BY-SA 3.0 via Commons.

In short, the system is pretty much the same, but is (usually) called slat in case of movable one and slot in case of fixed one.