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Concession from WikiPedia:

In politics, a concession is the act of a losing candidate publicly yielding to a winning candidate after an election, when the overall result of the vote has become clear.

Concession, per se, is entirely optional, and a candidate will sometimes refuse to concede defeat despite the vote count being against them, especially if they suspect electoral fraud. In that case the candidate would likely demand a recount of the votes or other investigations into the alleged fraud. Sometimes concession may be denied not because of any specific fraud allegations, but simply because of ill will accumulated over the campaign.

If the vote is relatively close, it can be unclear when it is appropriate for a losing candidate to concede an election. On election night, pressures from a media looking for news to report, an opposition campaign anxious to declare victory, and one's own campaign unwilling to concede defeat if there is any hope of a last-minute turnaround all weigh on the decision of the losing candidate. Though a spoken concession does not necessarily deny a candidate office if there is a drastic reversal in the vote count, it does practically prevent demands for recount.

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