"Risk-aware consensual kink" is a term that was coined in reaction to current dissatisfaction within the BDSM community regarding the political issues (internal and external) surrounding the "safe, sane and consensual" ethos that many people defines consensual BDSM. Specifically, RACK is intended to embrace edgeplay and play that is engaged in without safewords.
RACK is intended as a philosophy, and does not specifically refer to any particular type of play or activity.