What it isAirtime on a station or channel — read live, pre-recorded, or run as a video spot.
How it's boughtDirect with the station, through a rep firm, or programmatically where the channel is streamed.
When it's the right buyLocal radio is the cheapest live-read endorsement in advertising and nobody looks at it. Connected TV is the same ad spots bought like display — check which one a seller is actually quoting.
Lead timeDays on local radio; weeks on national television