The add-on makes a distinction between reminders and your todo list, so you can use the first to maintain a list of upcoming appointments, such as trips to the doctor, while the latter can be used to keep on top of projects that are not time-sensitive in the same way. The dialog that is used to configure new reminders and appointments is just a couple of clicks away, and any reminders that have been set up appear as pop ups in the lower corner of the screen. Sitting in the status bar, ReminderFox remains unobtrusive until it is needed. This is a browser add-on that provides you with access to your tasks, appointments and todos without the need for a separate application.
Google Calendar is a valuable tool for remembering appointments, but if you are looking for something that is more tightly integrated into your browser, ReminderFox may be just what you have been looking for. When you are using Firefox, there are numerous online calendars and todo tools you can use to keep track of the things you need to get done.