Jokers are not unrestricted wild tiles
In American Mah Jongg, a joker may substitute for some tiles in permitted groupings under the applicable rules. That does not mean it can replace any tile in any position. Specific restrictions apply, including the types of groupings for which jokers may be used.
A beginner should never assume that a joker can complete an arbitrary pair or that it is acceptable in every concealed or exposed combination. Check the official rules and your annual card.
Understand the context
When you see a teacher place a joker in a grouping, ask what kind of grouping it is and which rule permits that use. Understanding the reason is more helpful than memorizing one photograph.
The same visible tile may raise different questions depending on whether it appears in a permitted exposure, a concealed hand or another situation. That is why general statements such as “jokers are always good” are not sufficiently precise.
Joker exchanges need a demonstration
Some American play rules permit specific exchanges involving exposed jokers and matching natural tiles. These procedures are rule-sensitive. A guided demonstration using the current official rules is safer than copying a short online summary.
Ask your instructor to show when an exchange is allowed, who may perform it and how the relevant tile is handled. Do not interrupt a competitive game to experiment with an unfamiliar procedure.
Practice with examples, not guesses
During a teaching session, use your current card to review a few example situations and label them permitted or not permitted. Record the reasoning in your own words rather than copying copyrighted winning-hand patterns.
If you encounter contradictory advice online, check whether it refers to American Mah Jongg, another variant or an outdated set of rules.
This is independent educational information, not an official rulebook. For definitive American Mah Jongg play, consult your current official annual card and the rules used by your group.