doc: clarify that import also uses main

PR-URL: #41720
Reviewed-By: Geoffrey Booth <webadmin@geoffreybooth.com>
Reviewed-By: Mohammed Keyvanzadeh <mohammadkeyvanzade94@gmail.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

doc/api/packages.md

@@ -1138,17 +1138,19 @@ added: v0.4.0
 }
 ```
 
-The `"main"` field defines the script that is used when the [package directory
-is loaded via `require()`](modules.md#folders-as-modules). Its value
-is a path.
+The `"main"` field defines the entry point of a package when imported by name
+via a `node_modules` lookup.  Its value is a path.
+
+When a package has an [`"exports"`][] field, this will take precedence over the
+`"main"` field when importing the package by name.
+
+It also defines the script that is used when the [package directory is loaded
+via `require()`](modules.md#folders-as-modules).
 
 ```cjs
 require('./path/to/directory'); // This resolves to ./path/to/directory/main.js.
 ```
 
-When a package has an [`"exports"`][] field, this will take precedence over the
-`"main"` field when importing the package by name.
-
 ### `"packageManager"`
 
 <!-- YAML