For recurring tasks, the End date is the current occurrence — the recurrence repeats from it, and it moves forward when you mark the task as Done.

For Day(s) recurrence you can either choose your interval thru the use of the Every input or you can select on what day of the week the recurrence will repeat. In the event that you want to change your recurring options, make sure to always reset the option that you do not intent to use. Like set Every to zero if you intend to use Days of the week.

Task vs Events: Both repeat on the same schedule — the difference is what happens when you mark it Done. A Task is something you do each time: marking it Done rolls it forward to the next date, and past dates show as done. An Event is a fixed happening (a meeting, a shift) that just appears on each date and is never marked Done or moved.