The greater the two masses, the greater the attraction. Gravity is weak between small objects like people, but planets are massive enough to produce significant forces on near objects - gives you your weight. The smaller the distance, the greater the force. Newton was able to derive them using his physics and geometry. He was able to determine the shapes of other types of orbits mathematically related to ellipses.
Newtonian physics is a great triumph of the human mind.
It is still used today in uncountable ways, from aerospace engineering to the mechanics of athletic performance.