Core exercises are vital to building a strong foundation. Basically, the core is the area of then body that comprises the pelvic girdle, lumbar spine, hip joints, and abdomen. In order to do any other movements, such as a squat, the core must be able to support the movements in order to avoid injury.
Core stabilization can minimize movement of the vertebrae using small stabilizing muscles, such as the transverse abdominis, the diaphragm, and the pelvic floor muscles. The stability between the rib cage and the pelvis are also vital. Isometric exercises like bracing accomplish this stabilization.
What exercises are best? Exercise that incorporate stabilization are a good place to start. Planks, side planks, and bridges are good examples that require core stability. As core strength improves, exercises that are more dynamic can be added. Exercises like side bends, trunk rotation, back extension, and crunches incorporate more dynamic movements (flexion, extension, lateral flexion, and rotation). Also including resistance bands, medicine balls, kettlebells, and dumbbells can increase the challenge on the core as exercises progress.
Check out these core exercises from Ace Fitness:
:https://www.acefitness.org/resources/everyone/blog/5807/beginner-ab-core-exercises-to-increase-stabi