Explain the 'infer' keyword in the context of conditional types.

The 'infer' keyword allows you to declare a type variable within a conditional type's 'extends' clause to extract a specific type.

In advanced type manipulation, you often need to 'unwrap' a type—for example, getting the element type of an array or the return type of a function. The 'infer' keyword provides a way to ask TypeScript to guess what a type is during the evaluation of a conditional. It can only be used within the extends clause of a conditional type.