Dependent types are a concept in type theory where the type of a value can depend on that value itself. This means that types can be more expressive and can capture more information about the data they represent. For example, a type could specify that a list has a certain length, allowing for more precise type checking during programming. In programming languages that support dependent types, such as Agda or Idris, developers can write functions that ensure correctness by enforcing constraints at the type level. This leads to safer code, as many errors can be caught during compilation rather than at runtime, improving overall software reliability.