An exclusive window is a period a creator agrees to run only one brand in a given category, so a sponsor is not next to a direct competitor; it is a term two sides agree to, not a default.
A period during which a creator agrees to run only one brand in a given category, so a sponsor is not sitting next to a direct competitor on the same stream. It is a term two sides can agree to as part of a deal, not something imposed by default.
Exclusivity is one of the levers that makes a live placement worth more than a scattered impression: a brand can own a category on a creator's screen for a set stretch of time, with the creator's explicit agreement.