add small answer to types vs interface question

Author: tsiq-swyx

README.md

@@ -268,7 +268,17 @@ class App extends React.Component<AppProps, AppState> {
 }
 ```
 
-`interface`s are different from `type`s in Typescript, but for our purposes they do the same things. [read more](https://medium.com/@martin_hotell/interface-vs-type-alias-in-typescript-2-7-2a8f1777af4c)
+[Something to add? File an issue](https://github.com/sw-yx/react-typescript-cheatsheet/issues/new).
+
+## Types or Interfaces?
+
+`interface`s are different from `type`s in Typescript, but they can be used for very similar things as far as common React uses cases are concerned. Here's a helpful rule of thumb:
+
+- always use `interface` for public API's definition when authoring a library or 3rd party ambient type definitions.
+
+- consider using `type` for your React Component Props and State, because it is more constrained.
+
+[You can read more about the edge cases of using types and interfaces here](https://medium.com/@martin_hotell/interface-vs-type-alias-in-typescript-2-7-2a8f1777af4c). Note there have been significant changes since Typescript 2.1.
 
 [Something to add? File an issue](https://github.com/sw-yx/react-typescript-cheatsheet/issues/new).