What is a "reminder"?
Here is a list of few things that you might call a "reminder":
Shopping list
Christmas present list
To-do list
Alarm clock
Egg timer
Birthday reminder
Now, is there a single way to describe all of those things? Well, it may get wordy, but a reminder could be described as:
A notification message or sound that either appears automatically, or shows when you look for it, which is used to let you know that a certain time has passed, a moment has arrived, or that an outstanding task has not been completed.
See, pretty wordy. Breaking it down like that helps to see what features a reminders app will need to have. Before getting to that, let's test the definition against the examples from here
Shopping list: In this case, you go looking for the reminder, although we could set it up to automatically show when your location happens to be near the store! Other than that case, this is effectively a task that has not been completed.
Christmas present list: Much the same as a shopping list...
