Vertical and horizontal are two different ways to think about how things are arranged or positioned.
When we talk about something being vertical, it means that it is going up and down, straight up like a vertical line. Think about a flagpole - it stands straight up in the air, so it is vertical.
On the other hand, when we talk about something being horizontal, it means that it is going side to side, like a flat surface. Imagine lying down on the ground and looking out at the horizon - that line where the sky meets the earth is a horizontal line.
So basically, vertical means up and down, while horizontal means side to side. These terms can be used to describe things like lines, shapes, or even the way we are standing or sitting.