I'm assuming you haven't taken any physics courses, so let's start by explaining the concept of a force. Forces are the central focus of classical mechanics. Basically, a force is a push or pull on an object as a result of its interaction with another object. When applied to an object with mass, a force causes the object's to change in some way. Gravity is just the force of two masses attracting each other--in this case, the earth and your balanced pencil. The heavier side of the pencil has more mass, so the force of gravity on that side is stronger, causing it to "go down". There's actually a better explanation of this using rotational mechanics, but this should help!

I'm assuming you haven't taken any physics courses, so let's start by explaining the concept of a force. Forces are the central focus of classical mechanics. Basically, a force is a push or pull on an object as a result of its interaction with another object. When applied to an object with mass, a force causes the object's velocity to change in some way. Gravity is just the force of two masses attracting each other--in this case, the earth and your balanced pencil. The heavier side of the pencil has more mass, so the force of gravity on that side is stronger, causing it to "go down". There's actually a better explanation of this using rotational mechanics, but this should help!