I use simple machines every day. These are two of them.
One of them is a wheel and axle. I scooter a lot and the wheels on my scooter are the most important part. The wheel and axle rotate together and are both joined in the centre. The deck on my scooter is over 2 axles and that way the wheels can carry me. When I push on the road with one foot the scooter can roll me forward because of the wheel and axle. If I did not have a wheel on my scooter I would just scrape against the ground and I wouldn’t go anywhere.
Screws are everywhere. If there where no screws in this table I’m working at it would brake or fall apart. Everywhere there would be problems. If I opened a door it would fall off the hinges! If I screwed together two boards I would turn the screw (rotational force) and the screw would lift and push the boards strongly together (linear force). Screws are stronger than nails because the grooves make it so you can’t pull it out like a nail.