What is a plot hole?
A plot hole is a plot point that happens in a fictional story, such as a movie, that contradicts the established logic of the story. For example, if a character is established as being extremely selfish, but in one scene he gives money to another character in need for no apparent reason, this would be a plot hole as this development would not make sense to a reasonable audience member.

Most plot holes can still be explained if someone tries hard enough, but if the story does not give enough clues for an audience member to easily understand what is going on, it is a plot hole.

Plot holes have different effects on different people. Some people are taken out of the story when they notice a plot hole. Others never notice it. Still others notice plot holes or learn of them afterwards, but do not mind the plot holes.