That means it produces a native binary (for example, a .exe file on windows platforms), so ultimately you're aiming to run the program in a terminal. This is th

That means it produces a native binary (for example, a .exe file on windows platforms), so ultimately you're aiming to run the program in a terminal. This is the normal way for OCaml to operate. In this case the author is using Reason as an alternative syntax to OCaml. Reason resembles javascript a little more, and some people find that nicer to work with. So the idea is that you write Reason code, then translate it into OCaml code using the Reason tools, and then ultimately you compile it down to a native binary. If instead you want to write a web-app which runs in a web browser or node.js, then you'd need to compile it to Javascript, which is what bucklescript helps you do. Where does Rescript come in? As explained above, Reason can be used for writing either native apps or javascript apps. However, it's hard to evolve the syntax of Reason in a way which satisfies both aims. So they've now split the work -- going forward, Reason will specialize on native, and Rescript will specialize on javascript apps. Their syntax is expected to diverge from each other, in order to support those aims as best as they can.