Here's a breakdown:

* Eccentricity is a number between 0 and 1 (or sometimes expressed as a percentage) that tells us how much an orbit deviates from a perfect circle.

* 0 Eccentricity: A perfectly circular orbit.

* 1 Eccentricity: A highly elongated orbit, almost like a straight line.

* Values between 0 and 1: Elliptical orbits of varying degrees of elongation.

Think of it this way:

* A circle has the same distance from its center to any point on its edge.

* An ellipse has two focal points, and the sum of the distances from any point on the ellipse to the two focal points is constant.

The more eccentric an orbit is, the further apart the two focal points of the ellipse are, and the more elongated the orbit becomes.

Here's an example:

* Planets in our solar system generally have low eccentricities, meaning their orbits are fairly circular.

* Comets often have very high eccentricities, meaning their orbits are highly elongated. This is why they spend most of their time far from the Sun, then zoom past it quickly and head back out again.