The "Create Event Wizard" guides you through the setting up of a new event file.  The "wizard" is shown when you use the menu item  File  / New Event File.

On this page, the Wizard asks you to select the discipline for the event that you are going to work with.

You can select either "Foot Orienteering", "Mountain Bike Orienteering", "Ski Orienteering", or "Trail Orienteering".

In reality, any Condes event file can contain courses for all four disciplines.  Your selection does not set any limits to this.   However, your selection determines the default type of control and type of course when you create new controls and courses.

For example, for Ski-O events, the standard setting for controls is to have a dot at the center of the circle.  For other disciplines, you can still configure a control or a course to show a dot at the center of the circle, but you would have to do that explicitly.

Refer to Event Disciplines for more details.