A monologue is a speech delivered by one person, or a long one-sided conversation that makes you want to pull your hair out from boredom.
The Greek root word monologos translates to “speaking alone,” and that’s a monologue: one person doing all the talking. In theatre, sometimes a character has a monologue that they perform. You might have an internal monologue where you talk to yourself to better understand some dilemma. Some people talk forever in a constant monologue, never letting you speak. If two people talk back and forth, it’s a dialogue, which is different and probably more fun for everyone.