Here are some examples:
* A tall building stands vertically. The building is upright, not leaning or slanted.
* The flagpole was erected vertically. The flagpole is straight up and down, not at an angle.
* She held the book vertically. She was holding the book upright, with the spine facing her.
* The sun rises vertically in the east. While this isn't technically true due to Earth's tilt, we use "vertically" to describe the general direction of the rising sun.
* They climbed vertically up the cliff face. They were scaling the cliff straight up, not diagonally or horizontally.
Contrast with "Horizontally"
Vertically is the opposite of horizontally, which means parallel to the horizon (like a line across the surface of the earth).
* The rope stretched horizontally across the room.
* She pushed the box horizontally across the floor.
Think of it this way:
* Vertically is like a ladder going straight up.
* Horizontally is like a ladder lying flat on the ground.