The Earth's distance from the Sun is not constant because Earth's orbit is slightly elliptical. Here are the key measures:

* Average distance: 149.6 million kilometers (93 million miles)

* Perihelion (closest point): 147.1 million kilometers (91.4 million miles)

* Aphelion (farthest point): 152.1 million kilometers (94.5 million miles)

Astronomical terms:

* Astronomical Unit (AU): This is the standard unit for measuring distances within our solar system. 1 AU is defined as the average distance between the Earth and the Sun. So, Earth's average distance from the sun is 1 AU.

* Light-year: This is the distance light travels in one year. It's a much larger unit used for measuring distances between stars and galaxies.

Let me know if you'd like to know more about Earth's orbit!