1. A group of two: This is the most common meaning. It can refer to:
* Two people: "The duo performed a beautiful duet."
* Two things: "This coffee maker comes with a duo of mugs."
2. A musical piece for two performers: A duet is a musical composition written for two performers, typically singers.
3. A team of two: In video games and other competitive situations, a "duo" is a team consisting of two players.
4. A brand name: Duo is also a brand name for various products, including coffee makers, printers, and cell phone plans.
5. An adjective meaning "of two": You might see "duo-phonic" or "duo-lingual" to describe something that involves two sounds or two languages.
In short, "duo" usually refers to a group of two, but it can also be used in music, gaming, and as a brand name.