Hydraulic cylinders look like this on the inside:
The pin eye and clevis is where the cylinder is mounted to the appliance, and are the points between which the cylinder exerts its force.
The barrel is the body of the cylinder where the piston and rod can slide in and out.
The ports are where the hydraulic fluids are pressed in or out.
The wiper keeps dirt from reaching the gland. O rings seal the crevices between parts. the seals and wear rings keep the rod wear and leak free.
The nut keeps the rod securely attached to the rod.