Torque is a measure of rotating force. Commonly used for bolt fastening force and engine power. For fasteners that matter, the manufacturer will list a torque spec for that fastener. By using the correct torque the fastener won't break, strip, stretch, or come loose. (There are other rules you may need to follow in some applications like order of multiple fasteners or loctite) ELI5, 1 ft lb of torque is 1 lb of pressure applied to the end of a 1 ft lever. 50 ft lbs would be 50 lbs at the end of the same lever. For euro folks you may see Newton meters, same concept with metric units of length and pressure. To set your fastener to your goal value you will need a special tool. Torque wrenches are fancy ratchets that have an adjustable torque value. When you hit your selected value, they will click or beep depending on what kind you bought. There are also screwdrivers for lower values, those usually cam over at your selected torque. That means they slip inside and the handle turns without turning the fastener. Pro tips. On wrenches it is important to stop when it beeps or clicks, they will allow you to apply too much torque to the fastener if you keep going. Use steady force, jerking on the tool makes it easy to keep going past the beep or click and apply too much torque. Torque wrenches and screwdrivers should be used for tightening to a goal value only, never loosening. They are not to be used as a ratchet or screwdriver even though they could. Always reset the tool to 0 between uses, this helps keep the calibration accurate. Lots more to know but this enough to do better quality work. Usually I'd say enough to be dangerous but this genuinely makes the work you do safer, ever seen a wheel fall off on the side of the road? Wrong torque on the lug nuts.