What are the faded items on my calendar, and why will they not open?

They are recurring projections — a forecast of future occurrences of your repeating tasks and reminders. They are shown so you can see which weeks are already spoken for.

They cannot be opened because there is no record behind them yet. A repeating task becomes real on its due date; a repeating reminder becomes real once the current one is completed.

To hide them, untick Show recurring projections in the Filter Calendar popover. Your choice is remembered.