Muscle imbalances mean that the strength or the size of the muscle on one side of the body is different when compared to the same muscle on the other side. This issue is common and normal, especially for beginners who are new to bodybuilding.
Usually, muscles are bigger and stronger on the same side as your dominant hand as it tends to do more work. To correct this, you would need to practice perfect form when doing exercise. This way, both sides of your body will be putting in the same force in the movement. As well, you would need to concentrate on activating muscles on the weak side so that your dominant side is not doing all the work. And, you can perform extra sets of unilateral movements to target the underdeveloped area.
Check out the video below to see how you can test and correct this issue!