The Conferences module is an additional feature that you can use, in addition to the standard Course Group/Course/Class setup, that allows you to offer conference-type sessions.
Conferences are designed to be offered over a limited period of time, rather than every week. An example of a conference could be a weekend focus conference on a subject matter that is of interest to your clients. You might be a parks & recreation organization, offering ongoing athletic, arts, crafts, and enrichment classes. One weekend a season (or a year), you want to offer a craft intensive that people pay one fee for and attend multiple sessions over the weekend. Conferences allow you to set up multiple sessions with multiple options that your customers to register for.
This is an example of what conferences might look like on your ASAP public site. Note that 1 Conferences is available on the public left nav and the 2 conferences are available beneath that. Conferences may or may not have a 3 fee, slots may be 4 required or 5 optional, sessions may be chosen within the 6 time slots and sessions may or may not have 7 fees in addition to a conference fee.
Conferences can be used in addition to classes or instead of classes, depending on how your organization is set up.