What is the difference between "Learn" and "Ignore" in spell checkers

When right-clicking a word in Pages and Sublime Text, the user is offered to either "Learn" or "Ignore" the word. What is the difference between learning and ignoring? To me it would seem the same, that the word is simply "accepted" by the spell-checker and not highlighted as incorrect (red) anymore. But since it's two different choices, there's obviously a difference. Couldn't find information about this anywhere.