What is the italicized words that tells actors how to speak?

The italicized words that tell actors how to speak are called stage directions.

Here's why:

* Stage directions are instructions in a play that tell the actors how to move, speak, and express themselves. They are not meant to be spoken aloud by the actors.

* Italicization is often used to visually distinguish stage directions from the dialogue of the play.

Let me know if you'd like to see an example!