Every particle of matter in the Universe attracts every other particle with a force that is proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them. So let's try to understand what this law implies. To begin with it states that every particle of matter in the entire Universe is affected by this law. So the Sun, the planets, the Earth, people, cars, pencils, everything exerts and is affected by a gravitational force, hence the word Universal in the name of the Law. Now let's notice a peculiar thing about this gravitational force.
Newton claims that they exert an attractive force on each other.
This action at a distance is in fact a question that bothered Newton a lot, but he had no good explanation for it. Just like Kepler couldn't explain why the planets orbits were ellipses, Newton couldn't explain why the Sun and the Earth could exert a force on each other without touching. Now think of matter generating a gravitational field around itself and extending outward in all directions. Any other matter in the Universe then feels this field as a gravitational force. According to Newton's Law of Gravitation, the gravitational force between two objects is inversely proportional to the square of the distance between the two objects.