* Galaxy: A galaxy is a massive collection of stars, gas, dust, and dark matter, all held together by gravity. Our own galaxy, the Milky Way, is estimated to contain over 100 billion stars.

* Universe: The universe encompasses everything that exists, including all galaxies, planets, stars, and all matter and energy. It's vast beyond comprehension, and we don't even know how big it truly is.

Think of it like this:

* Galaxy: A single city, like New York City.

* Universe: The entire Earth.

So, a galaxy is a very small part of the universe.