Will this actually automatically make the contribution or will it only remind me to do it manually?
It s a reminder, you can set them to be automatic on a certain date, or have it remind you to enter it. Note this is only in Quicken, nothing is changing in the real world.
Reminders used to be called Scheduled Transactions, which more accurately describes their purpose. And as Chris pointed out, they can be used to remind you when you wanted to enter the transaction or to automatically enter the transaction on the date you specified.