There is a good description of the hammer die and anvil die on this link. A little ways down https://coinauctionshelp.com/mintingprocesshistory.html#.YDRaR2hKjIU
Ever seen a movie or video about a blacksmith? The anvil is the big piece of metal that doesn't move. The hammer is the little piece of metal that the blacksmith swings... Same basic deal. The hammer die strikes the coin, the anvil die just sits there and is struck.
I posted this coin to show everyone improvement on the right terminology of what's wrong with the coin
No problem. As stated.. It's a Misaligned Die Strike. That's when the Hammer Die (usually the Obverse die) is Misaligned when it strikes the blank.
it depends on how they orient the dies, on that cent it looks like the reverse was the on the anvil die the obverse was struck with the hammer die. the hammer die being slightly misaligned. Denver uses a horizontal press for speed. normally obverse is the hammer die, but the did switch it with the state and quarters since 2000 and the reverse being the hammer die and George being the anvil to strike up the design better. inverted die installation. FYI Buffalo nickels and Mercury dimes were the last 20th century issues to be struck exclusively with inverted dies. Inverted die installation isn't an error though, it's more of an alternate set up.
Both mints use horizontal presses and have since 2002. The 1986 cent is a nice example of a case where BOTH obv and rev dies are misaligned, the obv toward 3:00 and the rev toward about 5:30.
