Hiding Skill
Even though Hiding is not as strong a skill as it used to be, it is still useful. There are other ways to hide - casting the invisibility spell, using smoke/egg bombs, and in the future, drinking an invisibility potion. But using the hiding skill (activated from the skill list) hides you instantly and requires no other tool, item or resource. There are plenty of situations where it comes in handy. Unlike the invisibility spell, hiding with this skill does not wear off; you stay hidden until you make yourself visible again, or until someone detects you.
If you have been revealed, you cannot hide again for a short while (nor can you use another way of hiding, such as the invisibility spell).
The main drawbacks of using the hiding skill are that it can only be used once every 10 seconds, and that it cannot be used while you are in the line of sight of someone attacking you.
Besides being activated for normal use, having the hiding skill matters because it is a prerequisite for training the Stealth skill.
An attempt to hide inside a house does not depend on your skill level. Likewise, the hiding skill cannot be raised inside a house.
To raise your hiding skill, use it once every 10 seconds.