Qadha salaah

Please advise regarding Qadha Salaah , during a recent discussion the topic came up and certain people argued about the details of Qadha Salaah, so we would like to show in writing the exact details.
It was said that Qadha Salaah does NOT have to be made up , we should pay Fidya .
Please advise what the exact recourse is to make up for missed Salaah?