The word "proficiency"

Here, with easy words, I try to tell you the word "proficiency" used in the previous article.

For the word, the following is noted in the OALD;

"the ability to do something well because of training and practice."

Oxford Advanced Learner's Dictionary(OALD)

I would tell you, "I mean the word as
                         the skill level of getting better for the goal of a master skill."

That is my current proficiency for understanding the word. Even if wrong for real meaning, the meaning is what I hoped to tell you.

What meaning is the word "proficiency"? If you ask me that.