What is the difference between drag and thrust?

Answer 1

Increasing the power by advancing the throttle produces a marked difference in the rate of climb. Climb depends upon the reserve power or thrust. Reserve power is the available power over and above that required to maintain horizontal flight at a given speed. Thus, if an airplane is equipped with an engine which produces 200 total available horsepower and the airplane requires only 130 horsepower at a certain level flight speed, the power available for climb is 70 horsepower.

Although we sometimes use the terms "power" and "thrust" interchangeably, erroneously implying that they are synonymous, it is well to distinguish between the two when discussing climb performance. Work is the product of a force moving through a distance and is usually independent of time. Work is measured by several standards, the most common unit is called a "foot-pound." If a 1 pound mass is raised 1 foot, a work unit of 1 foot-pound has been performed. The common unit of mechanical power is horsepower; one horsepower is work equivalent to lifting 33,000 pounds a vertical distance of 1 foot in 1 minute. The term "power," implies work rate or units of work per unit of time, and as such is a function of the speed at which the force is developed. "Thrust," also a function of work, means the force which imparts a change in the velocity of a mass. This force is measured in pounds but has no element of time or rate. It can be said then, that during a steady climb, the rate of climb is a function of excess thrust.
The difference between thrust and drag is that thrust is to push something and drag is to pull on something.

Answer 2

Drag is a force that opposes an object's motion through a fluid (such as air or water), acting in the opposite direction to the object's motion. Thrust, on the other hand, is the force that propels an object forward through that fluid, typically generated by engines or propulsion systems. In simple terms, drag slows an object down, while thrust speeds it up.