1 everything that happened in the past, more specially since humans learned to write.
2 everything that got written down and was accepted as "the history" by some elite or another.
3 the field of study of 1 and 2. Discusses all kinds of explanations of what happened.
4 a school subject devoted almost exclusively to 2.
1 Johnny Cash is history.
2 The history of the colonization of America has little to do with what actually happened.
3 An interesting question in history is whether guns, diseases or beliefs were more important factors in eliminating the Native Americans.
4 History is quite boring, especially if it's about your own country.
The study of the past. 'History' is often used to mean 'historical knowledge' when in reality 'history' is the process of researching the past using the available evidence, cross referencing and establishing 'historical knowledge'.
Historians argue about whose interpretation is most valid. These debates often last decades and are only resolved when either one side's research is shown to be of poor quality, or when new evidence comes to light proving one interpretation more valid.
Postmodernists argue that history is rubbish because they reckon that it impossible to understand al the motivations of the creator of the surce material which 'history' uses to forge historical knowledge. They're wrong.
History: Hey, guys, i went though the archives and cross reference the kings accounts with his requests for money from Parliament.
Hitorical Knowledge: Hitler intended for WW2 to start, but not in 1939. His foriegn policy was ideologically driven.