​Spaying and neutering prevent unwanted litters, help protect against serious health problems, and may reduce many of the behavioral problems associated with the mating instinct.
 
Spaying: The removal of a uterus and ovaries
Neutering: The removal of testicles

Females who are not spayed are at risk of developing a pyometra (infection of the uterus). Chronic heat cycles/hormonal stimulation cause the uterus to become thickened and at a higher risk of bacterial infection. Females who get pyometra are normally very sick and require emergency surgery to remove the uterus. 

Neutering males can reduce the risk of prostate disease and testicular cancer. It can also makes your pet more affectionate and less likely to roam, get in fights, or become lost.

When should I spay or neuter?
Family Animal Care recommends spaying and neutering both kittens and puppies around 6 months of age. This recommendation is aligned with the AAHA guidelines for sterilization. Pets who are sterilized at this young age bounce back more quickly from surgery than their more mature counterparts.