All of the planets orbit the sun on approximately the same plane (since we started as a swirling pancake of gas and dust that eventually snowballed into planets, and then you and me). It looks like this: https://media.nationalgeographic.org/assets/photos/000/285/2...

If the orbital plane was a surface of water and the northern hemisphere is bobbing above the water, then up is perpendicular to the plane (away from the water, looking down on the top of Earth).