1st class
the fulcrum is between the effort force and the load. this lever is used for precision and power normally exerts a force on the load greater than the force you exert on the lever. it magnifies the force and changes direction
2nd class
the load is between the effort force and the fulcrum. used to exert a greater force on the load than the effort force on the lever. magnifies the force
3rd class
the effort force is between the fulcrum and the load. used to move a load quickly, you must exert a greater force on the lever than the lever exerts on the load. but in exchange the lever moves the load a greater distance