SSC is the motto of most of the BDSM community. Safe means that the activity is safe enough for all of the participants; risk has been minimized at least to the point where the benefit out ways the risk. It does not mean that it meets some third party's standard of safety. Sane generally means that the person is capable of giving informed consent. It is also expected that the activity does not pose a substantial risk to a participant's sanity. Consensual means that all participants have consented to the activity. The consent may be explicit or implicit and there may be blanket consent offered for a range of activities. There are many activities which may appear to be non-consensual (including "consensual non-consensual" scenes) but these are actually consensual