I know nothing about physics, but just finding that an orbit isn't that if a body has an elliptic orbit means it is accelerating and decelerating constantly dep

I know nothing about physics, but just finding that an orbit isn't that if a body has an elliptic orbit means it is accelerating and decelerating constantly depending where it is in the orbit? I guess it's quite easy to measure periapsis and apoapsis even for stars or planets that have a nearly circular orbit.