My old hobby-horse.
There is so much wrong with timeline events in Geni, I don't know where to start. Timeline events are an integral part of conventional genealogy, and Geni is the only site that does not support them.
The Projects feature was recently created/expanded to take the place of Timeline Events. An event such as 'The Alamo' would conventionally be created as a timeline event (not a Project), to which profiles are tagged. It would automatically be included in the relevant profiles and become an integral part of the tree.
The difference? Timeline Events are included in gedcom (because they are a standard genealogical approach, a part of the tree) - Projects are not. Both Geni import and export gedcoms will strip timeline events from the profile. No other site does this.
Generally, you get a better view of the profile if you are not a Geni member (that is, not logged in). This view includes the Timeline following the About section. A standard genealogical presentation. The main reason Timelines are not used in Geni is because their presentation is too obscure to members.
There is a problem with this view - the events are all over the place, and not in chronological sequence. I would like to see the calender from which they are created.
Dan. I would not advise using Timeline Events. Geni does not support them. Revisions? - there aren't any. Notifications? - there aren't any. Geni decided to develop Projects instead.