Static thrust means how much thrust is resulted from the prop spinning stationary. You can test this by mounting your engine in a stationary location, running the engine and taking a thrust reading on how much the engine is pulling. It will be different than dynamic thrust (which is the thrust that is seen in the air). If I remember right, static thrust values are always greater than dynamic thrust values.

But really, it doesn't really tell you much of anything. You can use that information along with the airframe drag characteristics, weight, rolling friction to estimate acceleration. And if you know liftoff speed, then you can estimate the takeoff roll, but you really don't need to know these things for a model airplane, unless you are in some sort of competition or something (which is why I know about it ).