The primary force that holds the earth in its orbit is the gravitational pull of the sun and the shape of that orbit approximates the shape of an ellipse but the elliptical shape is slightly deformed by the other planets in the solar system and all other bodies in the universe and even to a lesser extent by all of the energy in the universe (Since energy and mass are equivalent they both provide gravitational attraction.). If we disregard these minor effects on the orbit and just consider it to be an ellipse then the point to which the earth is attracted coincides precisely with the focus of the ellipse which is closest to the sun (An ellipse has two foci. One at each of its narrow ends.). Since we say the earth goes around the sun, you would think that this focus of the ellipse to which the earth is attracted would be located at the center of the sun, but this is not the case. When any body orbits another body, they actually orbit each other, since neither body is fixed in space. The common point they orbit about is somewhere along the line connecting their two centers and closer to the heavier one. With the earth and the sun, this point is somewhere below the surface of the sun but not at the center of the sun. The name for this point is the barycenter of the two body system. If gravity were a solid rod connecting the two bodies, the barycenter would be located along this rod at the balance point (think two people on a teeter totter). And so we see that the earth doesn't just go around the sun, but the earth and the sun go around each other!
This same thing is true of all the other seven planets and so there is a common barycenter for the sun and all eight planets. This common barycenter is not fixed at one location beneath the surface of the sun but moves around as the planets change their configuration. It is believed that this moving center of mass stirs up the sun and causes the eleven year sun spot cycle. A big clue to the truth of this is that Jupiter's year is eleven of our years and Jupiter is by far the heaviest of the eight planets.