Closing line value refers to the difference between the odds at which a bettor places a wager and the odds available at the time the event starts, specifically the final odds or "closing line." This concept is significant in sports betting as it reflects how the market views a particular bet at the end of the betting period. If a bettor secures odds that are better than the closing line, it indicates that they made a favorable bet since the market has moved in a way that suggests a lower probability of that outcome occurring.