Anyone who does something of value, any value, for someone or something other than themselves, that will be forgotten by most within nanoseconds but still, grand recognition of the event persists anyway because of the narcissistic nature of contemporary society. The requirements for earning this moniker were much more extensive in the 20th Century and earlier. Back then, you had to, like, save somebody from a fire to earn the title.

Defined in the movie Serenity:

A hero is someone who gets a lot of OTHER people killed.

Someone who helps without anything expected in return. Their gesture may be big or small, profound or not, it doesn't make im' any less of a hero.

one who lays down his own life so that others can live

A man or women willing to sacrifice themself to help others without the consideration of there own safety.
"Those who face fire without fear or armor.Those who step into the darkness without assurances of ever walking out again, because they know there are others waiting in the dark, Awaiting salvation."

A Submarine Sandwich. The long sandwich featuring layers of meat and cheese on a crusty Italian roll goes by a variety of names. Submarine, sub, and hero are widespread. Localized terms are bomber (upstate New York), wedge (downstate New York), hoagie (Delaware Valley, including Philadelphia and southern New Jersey), grinder (New England), Cuban sandwich (Miami), Italian sandwich (Maine), Italian (southern Midwest), and poor boy (New Orleans, before Katrina) now goes by soggy boy.

A valiant person; A submarine sandwich; A Chinese-American greeting word.

A person who voluntarily gives of themselves without expecting anything in return. In doing so they exhibit some sort of exceptional character trait. They also possess traits that make them a role model for others.