README: Add clarification of this repository's relation to OpenWrt buildroot

Signed-off-by: Ted Hess <thess@kitschensync.net>

README.md

@@ -2,10 +2,14 @@
 
 ## Description
 
-This is the OpenWrt "packages"-feed containing community-maintained packages.
+This is the OpenWrt "packages"-feed containing community-maintained build scripts, options and patches for applications, modules and libraries used within OpenWrt.
+
+Installation of pre-built packages is handled directly by the **opkg** utility within your running OpenWrt system or by using the [OpenWrt SDK](http://doc/howto/obtain.firmware.sdk) on a build system.
 
 ## Usage
 
+This repository is intended to be layered on-top of an OpenWrt buildroot. If you do not have an OpenWrt buildroot installed, see the documentation at: [OpenWrt Buildroot – Installation](http://wiki.openwrt.org/doc/howto/buildroot.exigence) on the OpenWrt support site.
+
 This feed is enabled by default. To install all its package definitions, run:
 ```
 ./scripts/feeds update packages