When a force moves an object, the force does work. The energy transferred is equal to the work done, and both are measured in joules (J). Work done is found with the equation work done = force × distance moved in the direction of the force, so W = F × d. One joule is the same as one newton metre (1 N m).
The work done by a force changes how energy is stored in the system. If you lift a box upwards, the lifting force does work and energy is transferred to the gravitational potential store of the box. If a car engine pushes the car forward and it speeds up, the work done goes to the kinetic store. If you stretch a spring, the work done goes to the elastic store.
If a force pushes a crate across a rough floor at a steady speed, the crate does not speed up or rise. The work done against friction is transferred to the thermal stores of the crate and the floor, and they warm up slightly.
Example: a force of 20 N pushes a trolley 5 m in the direction of the force. Work done = 20 N × 5 m = 100 J, so 100 J of energy is transferred. A force of 50 N moving an object 4 m transfers 200 J.