Type Guards are TypeScript features that allow you to narrow down the type of a variable within a conditional block of code. They are essentially runtime checks that inform the TypeScript compiler about the possible type of a value.

Type Guards are crucial for working with union types, `any`, or `unknown`. Without them, TypeScript can't accurately infer the different possible types a variable might hold, leading to potential runtime errors and less robust code.

Common Type Guards include `typeof`, `instanceof`, `in` operator, custom type guard functions (using the `is` keyword), and truthiness checks.

A custom type guard function is defined using the `is Type` syntax in its return type annotation. This tells TypeScript that if the function returns `true`, the checked variable can be treated as the specified `Type` within that scope.