The traditional definition of a “hero” is someone who is admired or idealized for courage, outstanding achievements, or noble qualities. A hero is someone who does something we couldn't do, don't want to do, or don't think we could possibly do.
If you are a hero, that usually means you have done good things to help other people. If you are a hero you would normally put others before yourself. A hero would normally put someone else's needs before their own in any circumstance.