The way you act when you're respectful, thoughtful, and kind towards others is politeness. It's politeness that makes you say "Thank you!" when someone hands you the pen you dropped.
Politeness and polite come from a Latin root, politus, which means "polished," but also "refined and elegant." Politeness is especially important in certain situations — politeness when meeting the Queen of England means a deep curtsy or bow, while politeness at your grandparents' house means saying "please" and volunteering to wash the dishes after dinner.