Castrations are desexing males. This is done with local anaesthetic and in some cases, under sedation. After this procedure is performed it reduces male behaviours as they are linked to testosterone. It is best to castrate animals at a young age before testosterone linked behaviours are developed.
If you have a male pet and do not intend to use it for breeding, then castration is strongly recommended. Castration does not only make male animals more manageable but also decreases the likelihood of many illnesses and diseases.