What is a Dyson Sphere?

Excuse me if this is a stupid question...
Would a dyson sphere cancel out gravity within the solar system? If u are trapping gravity around a star, no doubt the gravity would be weaker as a whole, so wouldnt the celestial bodies stray off course mainly because there is nothing to hold them in circulation?

No, because you can not trap gravity inside a sphere. If anything, the sphere would itself contribute to the mass in the center of the system (note that because of the symetrical shape and the properties of gravity as a force, it does not matter if the mass is evenly distributed over a sphere or located as a pointmass in to centre), thus keeping the planets in orbit.