i love eating dog food

So yesterday I was strolling along in some random park, and I saw this sign. And it said "Laughter is sunshine in a house". And it made me laugh really super hard. I was filled with sunshine in a house!! But I still don't really understand. Does it mean that when you laugh, it's like your body (a house) is being filled with sunshine? Please, any new insight on this wonderful quote would be muchly appreciated.
Save the giraffes!!