In Swift, the self keyword is used to refer to the current instance of a class, struct, or enum within its own methods or properties. When referring to properties or methods within the same class or struct, self can be omitted, as Swift will infer that you are referencing the current instance. However, using self explicitly can help clarify your code and make it more readable, especially in cases where you need to differentiate between instance properties and local variables with the same name.