When you're planning an activity (i.e. creating a Task), you have the option to make it a recurring Task.
This is configured for each Task record by a system (standard/default) field on the Task model called "Repeat Interval".
In the Profiles part of the "Data" Global Tool, you can choose whether this field is part of the "Create form" and/or "Preview" for Tasks.
However you create a Task - e.g. via the "Calendar" Home feature or clicking "Plan Activity" in a Company Full-Page Profile - you can then choose a value for "Repeat Interval" from the dropdown list.
After creating a repeating Task, the future-dated Tasks will not appear until the current Task has been marked as 'done' or 'ignored'.
The next planned activity (Task) is set from the latest Task date, one interval forward.
Some example scenarios:
Task is set to Apr 5, repeat interval set to monthly, I complete the task on Apr 8
Next task: May 5
Original recurring task set to Apr 5, repeat interval set to monthly, after a few months in August I change from Aug 5 to Aug 12 and complete
Next task: Sep 12
Note that it is the Task date and not the logged note date which sets the date for the next Task.
If you would like the planned activity to stop repeating after a while, just select "Don't repeat" on the most recently assigned Task.
Good to mention here that a Task always has to be associated with a Company.