In scientific research What is the control?

The control of an experiment is the part of an experiment that does not change, and is strictly used as a comparison to the variable that is being tested.
the control is what you don't change in the experiment.

Example: if i poured water on certain tapes (like Duct Tape and scotch tape) to see which one was the stickiest. My control would be how much water I poured on the tape. there can be more than one control and in this example the other two controls would be the length and the width of the tape.