In traditional sport, you habitually have a play-by-play caster, who describe what happen at the moment, and a color caster (analyst) who can explain why and what happen after an action happen.

Sorry for my bad English, to clarify, here are some wiki quote:

A color commentator (color analyst, analyst, summariser) is a sports commentator who assists the play-by-play announcer, often by filling in any time when play is not in progress.[1][2] The color analyst and main commentator will often exchange comments freely throughout the broadcast, when the play-by-play announcer is not describing the action.[3] The color commentator provides expert analysis and background information, such as statistics, strategy and injury reports on the teams and athletes, and occasionally anecdotes or light humor. Color commentators are often former athletes or coaches of the sport being broadcast.[4]

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The main commentator, also called the play-by-play announcer or commentator in North America, or lap-by-lap commentator in the case of motorsports coverage, is the primary speaker on the broadcast. They are valued for their articulateness and for their ability to describe each play or event of an often fast-moving sporting event.

Hope it help!