Here's a breakdown:

* Crystal: A solid material with a highly ordered, repeating arrangement of atoms, ions, or molecules.

* Unit cell: The smallest repeating unit that shows the three-dimensional arrangement of atoms within the crystal lattice. It's like a building block that, when repeated in all directions, creates the entire crystal structure.

Think of it like a wallpaper pattern – the unit cell is the basic design element that gets repeated to create the whole pattern.