The type of limits agreed to in certain BDSM role playing or sexual sessions.
No Limit - where the dominant is given a free reign, to do as they wish, which is not considered to be practical. In fact, it generally indicates the inexperience of those involved, when no limits are used.
It is also more for use in 'visual depictions' or 'text description' for entertainment type sites, promoting BDSM sex.
It can however, be used to signify a TPE (total power exchange) agreement.
Time Limit - simple time limit placed on how long any particular session will go on for.
Must Limit - Mainly a limit or wish list of procedures or acts, that have to be included in the sex session. If not completed, the session is usually extended, until the 'must limits' are met.
Soft Limit - A specified act that a submissive will perform, but only under very special circumstances. This is generally when the submissive is in a more heighten state of arousal, than normal.
The dominant is responsible for noting when or if, that state is achieved, prior to engaging in that 'special' sexual activity.
Generally, these sexual acts do not occur often. Only under special circumstances.
Hard Limit - is the deal breaker. These are acts and/or positions that one will not perform, under any circumstances. If these acts happen, it is supposed to end the session immediately.
Such limits can be someone claiming not to be into 'scat' and should that happen, can lead to termination of the session, and relationship.
These are the DEFINITIVE LIMITS of where a submissive WILL NOT GO.
Noteworthy: Limits are part of the negotiation process, prior to engaging in sex. It details what each is seeking, and willing to do. Crossing the line during a session is a huge NO NO.