Mars is named after the ancient Roman God of War. Mars looks red when viewed through a telescope and naming it after Mars is apt.
Mars is the planet that rules energy, competitiveness to suceed, action, passion, sexuality and force. It represents both ambition and desire, courage and strength. The main part of Mars energy is a person's sexuality - how they will use it and what stirs their passions.
Where Mars is placed in a person's chart shows how energetic, assertive and aggressive a person will be and how they will use their sexuality.
Basically Mars represents: