Pretend you're a robot. (I do this all the time, it's great!). Okay, are you pretending? Awesome! Now, take these colored blocks and BUILD ME A TURTLE, ROBOT!
If you're panicking right now, that's understandable. A general purpose robot would probably have no idea what a turtle was, much less how to build one out of blocks. There are ways that you could teach the robot about turtles and blocks, but you, being a human, are hopelessly flawed and would only be able to teach it your conception of what a turtle should look like and how to use blocks to make one. What the robot really needs is to be able to examine a bunch of different examples of a bunch of different turtles, and then use machine learning to choose the best, most reliable, and most efficient one to build. And rather than have you try and do that all on your own, researchers at the University of Washington are paying strangers to do it as part of a crowdsourced effort.