The language is easy to write, and what is oftem more important - to read.
Swift was developed by Apple and it’s easy to guess that it is designed for creating iOS apps. It is a general-purpose and multi-paradigm language and is intended to work with specific Apple development tools.
Swift is used to write apps for iOS, Linux, MacOS and all Apple accessories and devices. Even though iOS apps can be written with Objective-C as well, Swift remains number one choice among Apple developers.
What makes Swift the best for iOS:
Enhanced platform security
Support of dynamic libraries
Fast growing open source community.