Here's the breakdown:
* Focus: This is the point *inside* the Earth where the earthquake originates. It's where the rocks first rupture and cause the seismic waves.
* Epicenter: This is the point on the Earth's surface directly above the focus. It's the point where the earthquake's effects are typically strongest.
Think of it like this: The focus is like the spark that ignites the fire, and the epicenter is the spot directly above the fire where the heat is most intense.
