diff --git a/00-REPOTAG.md b/00-REPOTAG.md
index 0cab9c5..3d8175c 100644
--- a/00-REPOTAG.md
+++ b/00-REPOTAG.md
@@ -1,4 +1,24 @@
 The %{?repo} Tag
 ================
 
-Foo
+Most (but not all) RPM spec files will have a `Release` tag that contains
+the following:
+
+    Release:      %{?repo}N%{?dist}
+
+
+where `N` is *usually* either a positive integer or is of the form
+`0.rcM` or `0.devM` where `M` is an integer.
+
+The idea behind this added complexity to the `Release` tag is so that
+different repositories can exist that have duplicate packages sometimes
+even built from the same RPM spec file but with different capabilities.
+
+These repositories can then have a hierarchal `repo` macro so that as
+long as the `Version` is the same, the repository with the greater
+`repo` tag will always resolve as the newer package to RPM.
+
+This can help avoid things like GNU Emacs linked against X11 from being
+replaced by a GNU Emacs package that is not linked against X11 just
+because a “lower-level” package repository rebuilt GNU Emacs with a
+larger `N` than the “higher-level” package repository uses.