CPM is set by advertiser demand in an auction, so it varies enormously by niche, audience geography, and season. Content watched by purchase-ready adults in the US (personal finance, B2B software, insurance) commands high CPMs; content watched by teenagers globally commands low ones. Q4 CPMs spike with holiday ad budgets; January slumps.
Creators most often encounter CPM in YouTube Analytics, where it shows what advertisers paid on their videos. The number creators actually keep is better captured by RPM (revenue per mille), which accounts for the platform's revenue split and all income sources. In sponsorship pricing, "CPM" also gets borrowed as shorthand — brands sometimes price integrations at an agreed rate per thousand expected views.
