Disinfection removes most pathogenic organisms. Sterilisation is the killing or removal of all organisms (Science Direct).
Expanding on that, disinfection reduces the number of pathogenic microorganisms, such as viruses and bacteria, through inactivation.
Disinfection can reduce the level of contamination from bacterial endospores but it cannot kill them and it is this that differentiates disinfection from sterilisation. A bacterial endospore is a particularly tough and resilient structure that can lie dormant for a very long time.
Sterilisation destroys all pathogenic microorganisms, including vegetative endospores.
UV-C light has to be a wavelength of 260 nm to have maximal germicidal efficiency and to come anywhere close to comparing with sterilisation.