What is the eccentricity is planets orbit measure of?

Eccentricity is a measure of the deviation of a planet's orbit from being a perfect circle. It quantifies the shape of the orbit, with values ranging from 0 (a circular orbit) to 1 (a parabolic trajectory). A higher eccentricity indicates a more elongated, elliptical orbit. This parameter helps determine how varying distances from the sun affect a planet's climate and seasons.