A spay is a surgical procedure performed by a veterinarian that removes the ovaries and uterus from a female animal.
A neuter is a surgery performed by a licensed veterinarian that removes the testicles from a male animal.
Community cats live outside and are not friendly to people that they don't know. A community cat will run away when approached and will need to be trapped in order to be fixed. This is the safest way to provide care for these cats.