Short answers, pulled from the story.
Block programming is the arrangement of radio or television shows so that programs of a particular genre, theme, or target audience are grouped together and air consecutively. The goal is to attract a specific audience and hold them for an extended period.
NBC's "Must See TV" Thursday-evening lineup, built around Friends and ER, is one of the most prominent examples. Cartoon Network's Cartoon Cartoon Fridays, which aired premieres of the network's original series, is another widely cited case.
A marathon is a particularly long programming block, especially one that does not air on a regular schedule. The term is used when a block of related content extends well beyond a typical timeslot.
Commercial radio moved away from block programming because listeners expect a consistent type of music when they tune in, and switching formats risks losing them. Stations using mixed blocks historically struggled to build listener loyalty, since any given audience's preferred content aired for only a few hours each day.
Disney Jr., the Nick Jr. Channel, Boomerang, PBS Kids, and MeTV Toons all began as programming blocks before becoming full channels. Adult Swim remains a Cartoon Network programming block, and Nick at Nite's content later found a home on TV Land.
Public radio stations, including NPR, the BBC, and the CBC, continue to use block programming. Multicultural radio stations serving broad ethnic and cultural audiences also rely on the format, though even in these spaces block programming is declining due to competition for donations.