ELI5: Explain Like I'm 5

Lazy evaluation

Lazy evaluation is a way of doing things that gives you the same result, but takes less effort. It's like if you were walking to the store and your friend said, "hey, you don't have to walk all the way there, we can take the bus!" That's lazy evaluation: it's a way of getting the same result (getting to the store) with less effort (taking the bus instead of walking).