This is the 240th most frequent Japanese word.
登場
Appearance; entrance; introduction.
Here, "登場" is used to mean 'appearance' or 'entry' into a scene.
彼は映画の冒頭に登場します。
He appears at the beginning of the movie.
In this sentence, "登場" refers to the introduction or emergence of something new.
新しい製品が市場に登場した。
A new product hit the market.
Here, "登場" is used metaphorically for an idea or topic entering a discussion.