diff --git a/store/README b/store/README
index 8b003291723e..ab3829a7fef5 100644
--- a/store/README
+++ b/store/README
@@ -1 +1,5 @@
-Streams, mmaps, etc.
+The legacy .rdb format.
+
+Originally used for services and types .rdb files, before the former were
+replaced with XML files and the latter with the new binaryurp format, but still
+needed for backwards compatibility.