How to use AutoLayout in iOS
Auto layout is used to arrange views so that they look good on any device and orientation. Constraints are the rules that tell how everything should be laid down. They include pinning edges, centering, and setting sizes, among other things.
Auto layout is enabled by default, but you can double check this. If you click Main.storyboard in the Project Navigator and then show the File inspector. Make sure that Auto Layout and Size Classes are checked: