Add 'About Serena' contents to the intro page of the first section

docs/01-about/000_intro.md

@@ -1,3 +1,14 @@
 # About Serena
 
-In this section, we provide an overview of Serena, its purpose, and its key features.
+* Serena is a powerful **coding agent toolkit** capable of turning an LLM into a fully-featured agent that works
+  **directly on your codebase**.
+  Unlike most other tools, it is not tied to an LLM, framework or an interface, making it easy to use it in a variety of ways.
+* Serena provides essential **semantic code retrieval and editing tools** that are akin to an IDE's capabilities,
+  extracting code entities at the symbol level and exploiting relational structure.
+  When combined with an existing coding agent, these tools greatly enhance (token) efficiency.
+* Serena is **free & open-source**, enhancing the capabilities of LLMs you already have access to free of charge.
+
+Therefore, you can think of Serena as providing IDE-like tools to your LLM/coding agent.
+With it, the agent no longer needs to read entire files, perform grep-like searches or string replacements to find and
+edit the right code.
+Instead, it can use code-centred tools like `find_symbol`, `find_referencing_symbols` and `insert_after_symbol`.