docs/library/index: Elaborate uPy libraries intro.

docs/library/index.rst

@@ -9,34 +9,36 @@ MicroPython libraries
 
    * MicroPython implements a subset of Python functionality for each module.
    * To ease extensibility, MicroPython versions of standard Python modules
-     usually have ``u`` (micro) prefix.
+     usually have ``u`` ("micro") prefix.
    * Any particular MicroPython variant or port may miss any feature/function
-     described in this general documentation, due to resource constraints.
+     described in this general documentation (due to resource constraints or
+     other limitations).
 
 
 This chapter describes modules (function and class libraries) which are built
-into MicroPython. There are a few categories of modules:
+into MicroPython. There are a few categories of such modules:
 
 * Modules which implement a subset of standard Python functionality and are not
   intended to be extended by the user.
 * Modules which implement a subset of Python functionality, with a provision
   for extension by the user (via Python code).
 * Modules which implement MicroPython extensions to the Python standard libraries.
-* Modules specific to a particular port and thus not portable.
+* Modules specific to a particular `MicroPython port` and thus not portable.
 
-Note about the availability of modules and their contents: This documentation
+Note about the availability of the modules and their contents: This documentation
 in general aspires to describe all modules and functions/classes which are
-implemented in MicroPython. However, MicroPython is highly configurable, and
+implemented in MicroPython project. However, MicroPython is highly configurable, and
 each port to a particular board/embedded system makes available only a subset
 of MicroPython libraries. For officially supported ports, there is an effort
 to either filter out non-applicable items, or mark individual descriptions
 with "Availability:" clauses describing which ports provide a given feature.
+
 With that in mind, please still be warned that some functions/classes
-in a module (or even the entire module) described in this documentation may be
-unavailable in a particular build of MicroPython on a particular board. The
+in a module (or even the entire module) described in this documentation **may be
+unavailable** in a particular build of MicroPython on a particular system. The
 best place to find general information of the availability/non-availability
 of a particular feature is the "General Information" section which contains
-information pertaining to a specific port.
+information pertaining to a specific `MicroPython port`.
 
 Beyond the built-in libraries described in this documentation, many more
 modules from the Python standard library, as well as further MicroPython
@@ -58,9 +60,9 @@ what done by the `micropython-lib` project mentioned above).
 On some embedded platforms, where it may be cumbersome to add Python-level
 wrapper modules to achieve naming compatibility with CPython, micro-modules
 are available both by their u-name, and also by their non-u-name.  The
-non-u-name can be overridden by a file of that name in your package path.
-For example, ``import json`` will first search for a file ``json.py`` or
-directory ``json`` and load that package if it is found.  If nothing is found,
+non-u-name can be overridden by a file of that name in your library path (``sys.path``).
+For example, ``import json`` will first search for a file ``json.py`` (or package
+directory ``json``) and load that module if it is found.  If nothing is found,
 it will fallback to loading the built-in ``ujson`` module.
 
 .. only:: port_unix