The word "altruism" is defined as showing unselfish concern for the well-being of others, according to Dictionary.com. Giving money to charity, volunteering at a soup kitchen or helping a homeless person are examples of altruistic acts.
Altruism also has a related meaning in science. It refers to behaviors that may have no reproductive benefit and may even be detrimental to the individual performing the behavior, but the result is beneficial to the larger group with which the individual is associated.
An example is found in some wolf packs where a subordinate member helps care for the dominant wolf's offspring rather than spending that time mating and reproducing themselves.