[docs] Improve /styles vs /core/styles description (#16473)

docs/src/pages/customization/default-theme/default-theme.md

@@ -14,13 +14,3 @@ Please note that the documentation site is using a custom theme.
 
 If you want to learn more about how the theme is assembled, take a look at [`material-ui/style/createMuiTheme.js`](https://github.com/mui-org/material-ui/blob/master/packages/material-ui/src/styles/createMuiTheme.js),
 and the related imports which `createMuiTheme` uses.
-
-## @material-ui/core/styles vs @material-ui/styles
-
-Material-UI styles are powered by the [@material-ui/styles](/styles/basics/) npm package. It's a styling solution for React.
-This solution is [isolated](https://bundlephobia.com/result?p=@material-ui/styles), it has has no knowledge of the default Material-UI theme.
-To remove the need for injecting a theme in the React's context **systematically**, we are wrapping the style modules (`makeStyles`, `withStyles` and `styled`) with the default Material-UI theme:
-
-- `@material-ui/core/styles/makeStyles` wraps `@material-ui/styles/makeStyles`.
-- `@material-ui/core/styles/withStyles` wraps `@material-ui/styles/withStyles`.
-- `@material-ui/core/styles/styled` wraps `@material-ui/styles/styled`.

docs/src/pages/styles/basics/basics.md

@@ -202,3 +202,21 @@ const useStyles = makeStyles(theme => ({
 ```
 
 {{"demo": "pages/styles/basics/StressTest.js"}}
+
+## @material-ui/styles vs @material-ui/core/styles
+
+Material-UI styles are powered by the [@material-ui/styles](https://www.npmjs.com/package/@material-ui/styles) npm package (and JSS).
+This solution is [isolated](https://bundlephobia.com/result?p=@material-ui/styles), it does not know about the default Material-UI theme.
+It can be used to style React applications that are not using Material-UI framework.
+
+To remove the need for injecting a theme in the React's context **systematically** and to reduce the number of manual installations a developer needs to do, the `@material-ui/styles` modules are re-exported from `@material-ui/core/styles` (with a default theme).
+
+For instance:
+
+```js
+// Re-export with a default theme
+import { makeStyles } from '@material-ui/core/styles';
+
+// Original module
+import { makeStyles } from '@material-ui/styles';
+```