docs: added a bit of explanation to the meaning of each repo type

README.md

@@ -149,9 +149,9 @@ Arguments:
 * `options` (object, optional): may contain the following values
   * `lock` (string, defaults to `"fs"` in Node.js, `"memory"` in the browser): what type of lock to use. Lock has to be acquired when opening.
   * `storageBackends` (object, optional): may contain the following values, which should each be a class implementing the [datastore interface](https://github.com/ipfs/interface-datastore#readme):
-    * `root` (defaults to [`datastore-fs`](https://github.com/ipfs/js-datastore-fs#readme) in Node.js and [`datastore-level`](https://github.com/ipfs/js-datastore-level#readme) in the browser)
-    * `blocks` (defaults to [`datastore-fs`](https://github.com/ipfs/js-datastore-fs#readme) in Node.js and [`datastore-level`](https://github.com/ipfs/js-datastore-level#readme) in the browser)
-    * `datastore` (defaults to `datastore-level`)
+    * `root` (defaults to [`datastore-fs`](https://github.com/ipfs/js-datastore-fs#readme) in Node.js and [`datastore-level`](https://github.com/ipfs/js-datastore-level#readme) in the browser). Defines the back-end type used for gets and puts of values at the root (`repo.set()`, `repo.get()`)
+    * `blocks` (defaults to [`datastore-fs`](https://github.com/ipfs/js-datastore-fs#readme) in Node.js and [`datastore-level`](https://github.com/ipfs/js-datastore-level#readme) in the browser). Defines the back-end type used for gets and puts of values at `repo.blocks`.
+    * `datastore` (defaults to [`datastore-level`](https://github.com/ipfs/js-datastore-level#readme)). Defines the back-end type used as the key-valye store used for gets and puts of values at `repo.datastore`.
 
 ```js
 const repo = new Repo('path/to/repo')