A facade is the front of a building, or a kind of front people put up emotionally. If you're mad but acting happy, you're putting up a facade.
This word has to do with the outer layer of something. One sense has to do with the front or outside of a building. The other meaning has to do with people who are hiding something. In both cases, the facade could be deceiving. A building with a gorgeous facade isn't necessarily gorgeous inside. A person putting on a facade is definitely putting on a front: the face they're showing to the world doesn't match how they're feeling.