Here's why:

* Machines don't create energy: They can't make energy out of nothing.

* Machines transfer energy: They take energy in one form and transfer it to another form, often to do work.

* Machines change the direction or magnitude of a force: They help us apply forces more effectively.

Examples:

* Lever: A lever changes the direction of the force you apply (like a crowbar lifting a heavy rock).

* Pulley: A pulley changes the direction of the force and can reduce the amount of force needed (like a crane lifting a heavy object).

* Wheel and Axle: This system changes the magnitude of the force, allowing you to apply less force over a longer distance (like turning a steering wheel).

Let me know if you'd like to explore any of these examples in more detail!