Spoilers are detailed information that could make a quest too easy, give away part of the game plot or otherwise take the suspense/fun out of doing something. Some people want such spoilers to get past a frustrating section of the game, others would prefer just getting a hint so they know where to go next. That is the reason for the spoiler tag; when used properly it lets you highlight the text to read detailed descriptions, or skip them if you just want a hint.
