Machines are things people use to make life easier for ourselves. There are six classic "simple" machines, several of which have been used since the Stone Age.
This one is the most basic. It could be a hillside or a ramp. Maybe an entrance/exit to a freeway. It makes it easier to lift heavy objects up higher by pushing it up a slope rather than lifting the object up. It can also be used to move things downward easily, such as on a slide on a playground.
This is basically two triangular inclined planes back to back, designed to seperate stuff (Mr. Bruha's general purpose term for objects, materials, matter, etc). Big tough lumberjacks use them for splitting logs for the fireplace (with the classic steel wedge) after the logs have been chopped with an axe (a wedge with a handle). Contractors use them to seperate tile from floors. Gardeners use them to start a hole in the ground (this one's called a shovel). The ancient Egyptians used copper and wooden wedges to quarry massive stone blocks for building pyramids and obelisks. Even a nail has a tiny wedge on the end to seperate the fibers in wood so that the rest of the nail can squeeze inside a board.
A screw is really just round metal core with a thin inclined plane wrapped around it from the bottom. If you take a screw and touch the "ridge" at the bottom, then turn the screw in you hand (following the ridge with you finger), you will find that it is continuous the entire way up. This kind of simple machine can be used to fasten object together (your classic construction screw). It can also be used to move water inside a pipe or tube, such as with Achimedes' screw.
Wheel and Axle:
These are everywhere, from the waterwheels we made in class (the blue foam was the wheel, the wooden dowel was the axle) to the wheels of a car to the bottom of a skateboard. When the wheel turns, the axle turns in the same direction. When the axle turns, the wheel turns in the same direction.
This one is a thick wheel with a groove around the edge, with a rope (or string, or cable) going around the edge of the wheel (and held in place by the groove so it doesn't slip off). A pulley is used to redirect the force of pulling the rope, such as with lifting a heavy load up by pulling down on a rope going through a pulley, or by using the pulley to change the direction of the force, so a rope could be pulled smoothly around a corner with very little loss of energy. A limited number of wheels can be added to a pulley system to make work easier.
These are also seen everywhere. A see-saw (teeter-totter). A crow bar (pry bar). The back side of a hammer. A light switch. All are levers that move or turn on a point called the fulcrum. Adjusting the location of the fulcrum can make heavier loads easier to move, since a lighter weight on the long end of the lever can move a much heavier weight on the shorter end.