It's just the words, a 'control' is something that you have control over and can keep constant (or change intentionally) for every experiment.
A variable is something that can (but may not necessarily) change.
So if you were adding a drop of water to a beaker of a solution:
The drop of water is the 'Control'
The solution is the 'Variable'
A variable is something that can (but may not necessarily) change.
So if you were adding a drop of water to a beaker of a solution:
The drop of water is the 'Control'
The solution is the 'Variable'
