In biology, a control group is a group in an experiment that is not included in the procedure so that it can act as a standard for comparison. It is beneficial to have a control group as it makes the observations of the experiment more accurate.
1 Additional Answer
In simple terms, the control group is the group the group that is not treated or exposed to the things that others in the groups are. They are usually the group where nothing is done or a placebo is given.