diff --git a/ForumApp.markdown b/ForumApp.markdown
index 04c51c4..5c4423b 100644
--- a/ForumApp.markdown
+++ b/ForumApp.markdown
@@ -1,4 +1,4 @@
-ForumApp is a [BSP application](BSP) that synchronises forum posts among groups of devices.
+ForumApp is a [BSP application](BSP) that synchronises forum posts among groups of devices. Devices join forums by invitation.
 
 ### Channel identifiers