Universe refers to all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy.
The term "universe" can also mean:
1. A particular sphere of activity or experience (e.g., "the universe of fashion")
2. In mathematics, the universal set containing all elements under consideration
3. In philosophy, the totality of existence
Fun fact: The observable universe is estimated to contain 2 trillion galaxies!