Comment by blkhp19

I really like Grand Central Dispatch on iOS and OS X. You specify a task to run on a background queue or a main queue by passing a block of code. This block of code gets executed while the rest of the program continues. You can have completion blocks so you can respond to the completed task. The syntax is a little weird at first, but it's pretty powerful and I find it to be very explicit. Async/Await always confused me a bit.