A right-aligned editing instruction - CUT TO:, DISSOLVE TO: - between scenes.
Transitions are editor's notes: CUT TO:, SMASH CUT TO:, DISSOLVE TO:, FADE OUT. In a modern spec they're mostly redundant - a new scene heading already implies a cut - so each one you keep should be doing expressive work, like a SMASH CUT punchline.
Go deeper: Screenplay Formatting Basics
