Please tell me, what is equilibrium?

The term "equilibrium" can be classified into two classes, namely static equilibrium and dynamic equilibrium.

In Physics, the term "equilibrium" refers to "static equilibrium".  When all the forces (including turning forces) that act upon an object are balanced, then the object is said to be in a state of (static) equilibrium.  Referring to the photo, the scale is in a state of static equilibrium.

On the other hand, chemical equilibrium is a dynamic equilibrium.  At a state of chemical equilibrium, the forward and reverse reactions occur at the same time, and their rates are equal.  Referring to the photo, the scale is NOT in a state of dynamic equilibrium.

Yes, the scale is in equilibrium.  Equilibrium definition - a state of rest or balance due to the equal action of opposing forces.