Torque in practice
Torque is a turning force: force multiplied by the distance from the pivot. Tightening specifications for wheel nuts, spark plugs and bolts are given as torque, and so is engine output.
Metric specifications use newton-meters (N·m). US specifications use foot-pounds (ft·lbf) for larger fasteners and inch-pounds (in·lbf) for small ones; 1 ft·lbf equals 12 in·lbf. Older Japanese and European manuals often use kgf·m or kgf·cm.
Always convert to the unit printed on your torque wrench before tightening. Applying an inch-pound value on a foot-pound scale would overtighten the fastener twelve times.