What's the difference between a slot receiver and an outside receiver?

Chiefs WR Tyreek Hill is the No 1 slot receiver in the NFL per @NFL_DougFarrar

The slot receiver is typically lined up behind the line of scrimmage and inside another receiver Jamison Crowder plays this role for the Jets

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slot machine 888 slot receiver ' What is the difference between someone who projects as a slot receiver and a player who projects as an outside receiver? I