Eusocialism is the word for the social system of ants, some bee species, termites and naked mole rats. It stems from the words eu, which means good, and socialism, which has to do with living together. In biology eusocialism has no political meaning; it is just the word for a social system in which individuals work together with clear defined tasks for each individual and common goals. The most striking task devision in eusocial animals is reproduction. Only one or a few individuals reproduce, the others help raise these offspring.
This extreme division of labour in reproduction is enigmatic in biology, because genes are passed from offspring to parents. If there is a gene that makes you eusocial, making you raise the offspring of other individuals, how does it spread? Wouldn’t a sneaky gene that makes a worker ant produce offspring spread in the population?