Android - What's "creation mode" in the Galaxy S's offical messaging application?

From a Google search for "mms creation mode" I found this (among others) which says:

• MMS creation mode — Select Restricted to have your device prevent you from including content in multimedia messages that may not be supported by the network or the receiving device. To receive warnings about including such content, select Guided. To create a multimedia message with no restrictions on attachment type, select Free. If you select Restricted, creating multimedia presentations is not possible.