There were other things happening on 3 July 1863 during the Battle of Gettysburg, but they were for the most part overshadowed by "the big one", the Pickett-Pettigrew-Trimble Charge. Artillery bombardment for the charge went on from 1-3 p.m. (a few historians dispute that time frame) and was massive. At that time, 12,500 gray uniform-clad southern soldiers starting marching across an open field directly into enemy fire. And they kept coming. And falling. There was fighting on Culp's Hill on the 3rd, and some cavalry action that day as well. Stuart's and Custer's cavalry units had their battle at East Cavalry field on this day.
