Conditional activities (or conditional release) restrict the availability of an activity according to certain criteria such as dates, grade obtained, prior activities being completed. This is a useful strategy for self paced or
blended learning design, for example.
Completion tracking has to be enabled on course settings for this to work. When it is you will see 'Restrict access' option in any of the activity settings.
See attached pdf for an overview of how this works.
Also please note that Conditional activities do not work with groups.
If you are going to use conditional activities, it is really important that you plan it out carefully before you set your course up, if you are in any doubt at all, the members of TaLIC would be more than happy to support you please get in touch at email@example.com