Whatever activity you are completing, be it tying your shoelaces or reaching up to a shelf. Your core is being used in some way to help you with your movement. Each muscle provides a different function to help work together to provide a seamless motion through out our day to day tasks.

There is more to your core than just your abdominal muscles. your core is made up of:
Erector spinae. The erector spinae is a back muscle which helps extend your trunk. In easier words it helps you stand up straight after bending over.
Exercises: Supermans
Exercise: Bird dogs
Obliques. Your Internal and external obliques work together to help you flex/bend the torso forward and sideways and rotating the torso to the right/left.
Exercises: Russian twists
Heel touches
Rectus abdominals. The good old ‘six pack muscles’. These are what most people refer to when they say abs or core, they mean the rectus abdominals. These muscles help you bend forward.
Exercises: Crunches
Exercises: Butterfly sit ups
Transverse abdominis. These muscles wrap around the front and the side of your trunk. They provide stability to your thoracic and pelvis area.
Exercises: Plank
Exercise: Bicycle crunch
Multifidus. This provides stability, support and stiffness to the spinal column, allowing each disc to work more efficiently.
Exercises: Superman plank
Try this core workout for yourself
Beginner: 3 rounds Intermediate: 4 rounds Advanced: 5 rounds
Complete each exercise for 20 seconds followed by 10 seconds rest between each.
Crunches
High knees
Russian twists
Squat jumps
Plank
Mountain climbers
Glute bridge
Bird dog