Marx burrowed the idea of history from Hegel.

For Marx history is the process of social changes. When that process of changes reaches it's end, you have Marx's end of history. For Marx that's a communist society in which all workers get equal pay and life happily ever after. Afterwards there are no social changes, therefore there's no history.

Marx makes a prediction that this communist society will come about. Things that move the world closer to that prediction are morally good for Marx.