add extra parameters info

Author: sparklyballs

README.md

@@ -36,7 +36,13 @@ docker create \
 linuxserver/plex
 ```
 
-**Parameters**
+## Parameters
+
+`The parameters are split into two halves, separated by a colon, the left hand side representing the host and the right the container side. 
+For example with a port -p external:internal - what this shows is the port mapping from internal to external of the container.
+So -p 8080:80 would expose port 80 from inside the container to be accessible from the host's IP on port 8080
+http://192.168.x.x:8080 would show you what's running INSIDE the container on port 80.`
+
 
 * `--net=host` - Shares host networking with container, **required**.
 * `-v /config` - Plex library location. *This can grow very large, 50gb+ is likely for a large collection.*