What is a coin re strike?

A restrike is a coin that is minted later than what the date says on it. For example, all examples of the Maria Therisa Thaler from 1780 onwards are dated 1780, and the Austrian mint still produces them today, but they are all dated 1780. Re-strikes are not the same as reproduction coins because re-strikes are either authorized by the mint that first produced them (as in the case of the thaler) or struck from authentic dies later on (as in confederate half dollar restrikes). It is important to know if a coin you are buying is a restrike or not if you are looking for a particularly old coin, because some less knowledgeable or fraudulent dealers will make the date on the coin a major selling point, despite the coin not being struck in that date.