--actually they are used in real life. parabolas are seen in "parabolic microphones" or satellites. and there are others for both ellipses and hyperbolas.
Circles, parabolas, ellipses,and hyperbolas are called conic sections because you can get those shapes by placing two cones - one on top of the other - with only the tip touching, and then you cut...
A : A circle is a closed figure with eccentricity 1. Similarly, ellipse is also a closed fig with eccentricity less than 1 and parabola with greater than 1.