Screenwriting is the process of writing scripts for movies, TV shows, or plays. A script is a blueprint that tells the story, including what the characters say (dialogue), what they do (actions), and how the scenes unfold.
Acting is the art of portraying a character in a play, movie, TV show, or any other performance. An actor takes on the personality, emotions, and behavior of someone else (a character) and brings them to life for an audience.