That's the mutual gravitational attraction between the sun and the earth.
gravity
Gravity and Inertia
Objects are held in their orbits by the force of gravity. The Moon moves round the Earth but is continuously being accelerated towards the Earth by the mutual force of gravity. Because the Moon is lighter, it moves more noticeably. The acceleration caused by the force makes the Moon continuously curve towards the Earth but its high speed prevents it falling inwards. That is how an orbit happens.
Because the force due to universal gravitation that attracts the earth and sun toward each otherbends the earth's motion into a curve.That prevents the earth from moving in a straight line, as it would if there were no force of gravity.
an orbit is the circular movement of a planet going round the sun, or a moon going round a planet. Gravitaional force is what creates the orbit.
The Earth's gravitation force is greater than the Moon, which keeps the Moon in orbit round the Earth.
There are no planets orbiting the Earth because all eight of them orbit the Sun. But the Moon orbits the Earth, and all it does is go round and round in a rather complicated orbit which is disturbed by the Sun's gravity.
One complete round of Earth on its orbit around the Sun is called a "year." It takes approximately 365.25 days for Earth to complete one orbit.
The function describing earth's orbit round the sun is that for an ellipse.
Rather simplified: one orbit of the Earth round the Sun is a year. One rotation of the Earth on its axis is a day and a night of 24 hours.
The moon does orbit the sun. The moon orbits round the earth, while both earth and the moon orbits round the sun.
An orbit is the path followed by a planet as it travels regularly round the Sun. The Earth follows an orbit and completes one journey round its orbit in a year.