Some actuators use pressure -- either fluid or gaseous -- to generate an output force. These are commonly known as pneumatics or hydraulics, and are seen in applications ranging from manufacturing to dentistry, automotive, entertainment, and more.
Pneumatic artificial muscles (PAM's) are a special case of pneumatics that can move non-linearly and generate forces much like those of natural human muscle. The McKibben actuator is a subset of PAM's, which use a woven sheath in order to direct the change in shape and force output of the pneumatic tubing.
Left: Our McKibben design in action, March 2021