📝 Improve explanation of request bodies

docs/tutorial/body.md

@@ -1,4 +1,15 @@
-To declare a request body, you use <a href="https://pydantic-docs.helpmanual.io/" target="_blank">Pydantic</a> models with all their power and benefits.
+When you need to send data from a client (let's say, a browser) to your API, you send it as a **request body**.
+
+A **request** body is data sent by the client to your API. A **response** body is the data your API sends to the client.
+
+Your API almost always has to send a **response** body. But clients don't necessarily need to send **request** bodies all the time.
+
+To declare a **request** body, you use <a href="https://pydantic-docs.helpmanual.io/" target="_blank">Pydantic</a> models with all their power and benefits.
+
+!!! info
+    You cannot send a request body using a `GET` operation (HTTP method).
+
+    To send data, you have to use one of: `POST` (the more common), `PUT`, `DELETE` or `PATCH`.
 
 ## Import Pydantic's `BaseModel`
 

docs/tutorial/intro.md

@@ -39,13 +39,13 @@ pip install fastapi[all]
     
     This is what you would probably do once you want to deploy your application to production:
 
-    ```bash
+    ```
     pip install fastapi
     ```
 
     Also install `uvicorn` to work as the server:
 
-    ```bash
+    ```
     pip install uvicorn
     ```