Earth actually tries to enter into sun ,but as earth come closer to sun, speed of earth increases ,and earth escape from falling into it.
Earth revolve around sun because there are many planets who operate force on the earth at the same time sun also operate force on the earth,but force due to sun is dominating and so instead of moving straight towards sun it revolve around sun as planet forces also operate on the earth. And hence it is not move in perfect circular orbit bt in elliptical because magnitude of forces varies from place to place.
According to fundamental law of motion nothing is stationary. Two body central force concept explains that every system in this universe revolves around some point. Not only earth but sun and even our galaxy too revolve about some non matter point in space and this is because of conservation of angular momentum. Concept of centripetal force is corollary to concept of angular momentum conservation.