Imagine you're playing with a toy car. If you start moving the car, that is the "beginning" of the action of "driving" the car. In grammar, we call this "starting" or "beginning" stage the inchoative aspect. It is used when we want to describe that an action has just started or is beginning to happen.
For example, let's say you're learning Spanish and you want to say "I am starting to run." In Spanish, you could use the inchoative aspect by saying "estoy empezando a correr." The word "empezando" means "starting" or "beginning," so this sentence means "I am starting to run."
Overall, the inchoative aspect is used in grammar to describe the beginning or starting stage of an action, just like the moment when you start moving your toy car.