ReScript is specifically ReasonML with Bucklescript, which is for transpiling down to Javascript. They also made a few minor syntax changes that make it look a bit more like Typescript.

I think it's just when you use ReasonML in conjunction with Bucklescript to target JS. If you're using ReasonML to compile natively then things are the same.

I'm even more confused.

It's like all of BuckleScript and parts of ReasonML is now ReScript. Except BuckleScript has a new C-like syntax unlike the ML syntax that made BuckleScript BuckleScript as opposed to ReasonML.

Basically Bucklescript have forked their own (very similar) syntax from ReasonML and branded the whole syntax + Bucklescript + compiler package as ReScript. I suppose the goal is to eliminate the confusion of having so many moving parts and unify them all under a single ReScript brand.

Thanks. I guess the thing I didn't understand was where this leaves Reason: what is left under the Reason banner? But a fork would explain the overlap.

Lots of things are under the Reason banner:

- The Reason syntax at https://github.com/facebook/reason

- Esy, the npm-like Opam-compatible package manager at https://esy.sh/

- Reason native tooling in https://reason-native.com/

- Not forgetting that Dune and Odoc, two standard tools in the OCaml ecosystem, both support Reason syntax.

EDIT: and I forgot about the various editor plugins which provide Reason support, the most well-known is probably https://marketplace.visualstudio.com/items?itemName=jaredly....

Reason is still an alternative syntax to OCaml for native development, although I have no idea how many people actually use it for that.