Different exercises require different techniques, for example a cardio exercise may be a matter of completing the exercise for a certain duration, at a certain intensity.
In general:
Reps: repetitions. The amount of times that an exercise needs to be repeated.
Sets: the amount of time that the entire exercise, with all its repetitions, needs to be repeated.
Hold: the number of seconds (or minutes) that you need to hold a certain position.
Duration: the length in minutes that you need to be doing this exercise, usually used for cardio exercises such as running or swimming.