Broadly speaking, modules (aka portals) refer to the area of Event Cloud in which your users prepare for your event. Each module is specific to a user type; within each module, your users have a scope of visibility that is specific to their role. For example, users with the Admin role will have significantly more capabilities in the Admin portal than a user with the Speaker role in the Speaker portal.
Keep in mind that some users are given more than one role. If you have multiple roles, you can toggle between them easily.
Notice the drop-down menu in the top right corner of your event site. Click the down arrow to open up the menu:
Selecting an option will reload the page from a different user module (if applicable). From there, you can make any necessary preparations for your event.