# FoundationDB Authors - FoundationDB Flow (Highlights)  ## Highlights - The sender holds a `Promise<X>` to, sometime in the future, deliver a value of type `X` to the holder of the `Future<X>`. ([View Highlight](https://read.readwise.io/read/01kv6wyrt3rajbwj1xz6wexa42)) ^1025665807 Promise is used to resolve or reject the Future. - To use the `wait()` statement, a function needs to be declared as an ACTOR function, a special flow keyword which directs the flow compiler to create the necessary internal callbacks, etc. ([View Highlight](https://read.readwise.io/read/01kv6x0b0ndrfshvha32w8ragv)) ^1025666004