# Core Data Types

> Foundational data types for ZIO applications including effect values, type aliases, runtime execution, exit values, and failure causes.

In this section we are going to talk about the basic data types that are required to build a ZIO application:

- **[ZIO](zio/zio.md)** — `ZIO` is a value that models an effectful program, which might fail or succeed.
    + **[UIO](zio/uio.md)** — `UIO[A]` is a type alias for `ZIO[Any, Nothing, A]`.
    + **[URIO](zio/urio.md)** — `URIO[R, A]` is a type alias for `ZIO[R, Nothing, A]`.
    + **[Task](zio/task.md)** — `Task[A]` is a type alias for `ZIO[Any, Throwable, A]`.
    + **[RIO](zio/rio.md)** — `RIO[R, A]` is a type alias for `ZIO[R, Throwable, A]`.
    + **[IO](zio/io.md)** — `IO[E, A]` is a type alias for `ZIO[Any, E, A]`.
- **[ZIOApp](zioapp.md)** — `ZIOApp` and the `ZIOAppDefault` are entry points for ZIO applications.
- **[Runtime](runtime.md)** — `Runtime[R]` is capable of executing tasks within an environment `R`.
- **[Exit](exit.md)** — `Exit[E, A]` describes the result of executing an `IO` value.
- **[Cause](cause.md)** — `Cause[E]` is a description of a full story of a fiber failure.