Movement is also called locomotion. This is a life process. Movement allows an organism to seek shelter, escape predation, find nutrients and to find mates. It allows living things to react to stimuli in the environment by responding. Movement is accomplished by the skeletal-muscular system in humans. Voluntary and involuntary muscles are stimulated by nerves to contract or relax and these in turn pull on bones, which causes movement. Tendons connect muscles to bones. Cartilage protects bones in the joints from rubbing together. Some living things have muscles without an endoskeleton. They might have an exoskeleton like Arthropods do. Or, they may lack a skeleton completely--like earthworms do. If they are complex, their muscles cells will carry out movement. However, unicellular protists and bacteria can move by the action of flagella, or cilia or pseudopods. Even plants can move in the direction of light, water and gravity. These movements are directed by the effect of plant hormones called auxins that cause growth of plant cells in a certain direction.
Movement in biological terms is defined as: an action by an organism or part of an organism that causes a change in position or place.