rotation

The plane rotates to takeoff pitch.

Instead of pointing straight at the horizion (level) it starts to rotate to about 10' pitch, and then onto about 18 after positive rate of climb is established

Rotation is the action of rotating the aircraft against the lateral (pitch) axis

Thank you for the explanations. I still think it is a confusing term though!

Actually, rotate is a precise term and is intended not to confuse but to explain. One of the areas of knowledge real pilots must master then understand for each flight is weight and balance. In the context of this discussion, weight is not pertinent and will be ignored. Balance, however, is pertinent. Every aircraft, in every weight and loading configuration, has a point called center of balance. Theoretically, if you could precisely locate that point and the pencil could bear the load, you could balance the aircraft on the point of a pencil by lifting at that point. If you want an example, you can do the same trick using a ruler.

There are lines of axis that run through that balance point for both pitch and roll. When an aircradt reaches takeoff speed, the pilot can then "rotate" the nose sufficiently above the pitch line of axis, changing the airfoil's angle of attack, and allowing the aircraft to fly.

While this may be more of a detailed discussion than you were asking for, the only reason you were confused by the term "rotate" is that you did not have the underlying knowledge to allow you to understand it. Now you do.