1. Gravity: This force pulls objects towards each other. On Earth, it's the reason objects fall to the ground and why we stay anchored to the planet. It affects the motion of planets, stars, and galaxies.

2. Friction: This force opposes motion between surfaces in contact. It can be caused by the roughness of the surfaces or the attraction between molecules. Friction slows down moving objects, and it's what allows us to walk, drive, and even hold onto objects.