- Error handling is the process of responding to and recovering from error conditions in your program. Swift also has built-in support for throwing, catching, propagating and manipulating errors. This is very useful especially when writing asynchronous code, because what might happen at some point is that some operations won't always complete execution or give you a useful output, and without catching errors, you won't be able to know what happened and/or find out where it exactly happen in your Application.