The minor edit option allows an editor to mark a given edit as "minor". Each editor determines whether the edit is "minor" using their good judgment.
Marking an edit as "minor" helps other users manage what they view in their watchlists, the recent changes page, or the page history. Some editors may even set their preferences to exclude minor edits from their watchlist for efficiency, reducing the number of changes they have to review.
For this reason, users should only mark an edit as "minor" if no one would ever disagree with it: for instance, correcting a typo or adding an internal link to another article. If your edit changes the meaning of the entry, even a little bit, please save it as an ordinary edit rather than marking it "minor".