Trap, neuter, vaccinate, return, or "TNVR" is the act of
catching a stray/feral cat from a colony, having it spayed or neutered,
vaccinated, and then returning it back to where it was found.
Making sure that feral colonies are vaccinated and spayed/neutered helps
many issues, including:
Community Cat groups exist in many towns to help locals with trapping their feral cats, and getting them appointments at veterinarians who usually offer discounted services to help the cause.