In this article, Barney Waiganjo explains how to add keyframe animations to iOS apps using Swift 4. Keyframe animations are a sequence of subanimations that are combined to form one larger complex animation, with timing defined relative to the duration of the overall animation. The author provides a step-by-step guide on how to create a simple keyframe animation by adding subanimations inside an `animateKeyframes` closure, specifying parameters such as relative start time and duration, and combining them to achieve a desired effect. With this tutorial, developers can learn to create complex animations using keyframe animations, which can be used in various iOS app projects, and explore more about iOS animations through other posts by the author.