Toyota Safety Sense (TSS) is the name given to a suite of technology features that provide advanced collision mitigation and avoidance on Toyota vehicles. TSS is closely related to the Lexus Safety System+ because of the close corporate relationship between the brands.
Generally speaking, TSS is an advanced driver assistance system (ADAS), though that term encompasses more features than are present in TSS. The intention of any ADAS is to reduce the chance of a collision or road departure, and if an accident is unavoidable, to reduce the damage as much as possible. Since most traffic collisions and accidents are the result of human error, ADAS systems try to make the car easier to drive and warn the driver when errors are happening. Toyotas sold in America since 2016 generally have one of three versions of TSS. Those are TSS-C, TSS-P, or TSS 2.0. Check your Toyota's owner's manual or ask your dealer which system your vehicle may have.