What's the difference between a rinse-out conditioner, a deep conditioner, and a hair mask?

A rinse-out conditioner is the daily-use product applied after shampoo and rinsed within a minute or two. Deep conditioners and masks are richer, applied less often (typically once a week), and left on for 5–20 minutes to drive moisture or protein further into the cuticle. Many shoppers use both: a daily rinse-out plus a weekly mask.