Torque is a turning force: force times the length of the lever arm. Engine torque and bolt tightening specs are given in newton-meters in metric countries and in pound-feet (often called foot-pounds) in the US. Small fasteners use pound-inches. Getting this conversion right matters: overtightening a wheel nut or a carbon bike part by 35% is easy when lb·ft and N·m are confused.
Use the converter above for any pair. The most searched pairs have their own pages with worked examples and reference tables, listed above.