There are several GEDCOM-defined tags which have "special places" when editing a profile (such things as birth, death, occupation, education).
However, there are other GEDCOM "event-type" tags which do not currently have any means to associate data with them. The proposal is to use the "Add Event" feature of the Timeline tab to have "pre-defined" titles for those other "GEDCOM events". Over time, those pre-defined 'events' could have additional or other "pre-defined" fields appropriate to them. However, just by using "standard names" for such GEDCOM-defined events would allow more consistent interchange of data between GENI.COM and local desktop genealogical software.
See this topic for related discussion (from which this request arose): http://www.geni.com/discussions/99969