I know absolutely bugger all about airplane design and this is probably a really idiotic question but bear with me. Of late I've noticed that a lot of commercial airliners now have these weird flippy things on the ends of their wings. Most of them look like someone took the last section of the wing and bent it 90° up and some of them look like they just tacked on a small vertical section at the end of the wing. What the heck are these things and what are they for???