The newton (symbol: N) is the International System of Units (SI) derived unit of force. It is defined as 1 kg m/s^2, the force which gives a mass of 1 kilogram an acceleration of 1 metre per second. It is named after Isaac Newton in recognition of his work on classical mechanics, specifically Newton's second law of motion.
At average gravity on Earth, a kilogram mass exerts a force of about 9.8 newtons. An average-sized apple exerts about one newton of force at Earth's surface, which we measure as the apple's weight on Earth.