What is the significance of a control group in a scientific experiment?

i need a short answer of that question, if it is possible. Thank you|||You have a control to use as a basis of comparison. so that you can see what your results mean. If you do an experiment, and get results without a control, you wouldn't know how the results are different from a normal environment.|||It 'controls' for unexpected or unknown variables. If you are testing a toxin, the control would have the same of everything except the toxin. If some in the control die, you have to assume that some in the test would also have died from these uncontrolled causes.