According to the Wikipedia article on the Battle of Gettysburg, after that battle Robert E. Lee stopped making offensive maneuvers and rather started reacting to Union offensives. Is this 100% true, or were there other maneuvers? Also, why did he stop making any offensive maneuvers after the battle?
Gettysburg was pretty much a last ditch effort by Lee and Jefferson Davis to save the Confederacy or at least give it some credibility. There were different objectives that led to the attack in the first place. For one thing, the war in the West was going against the Confederates, and if the West fell, and more importantly access to the Mississippi River, then opportunities for resupply would be lost.
Another consideration was that by obtaining a victory at Gettysburg, Lee and his army would be poised to threaten Philadelphia and New York. They would also have access to fresh farmland and supplies that they could take from the North, rather than being so dependent on the already depleted resources of Virginia and the rest of the South. By threatening two of the largest Northern cities, Lee would have been in a position to petition for a peace plan that would have led to the true and permanent separation of the US into two different countries.
Lastly, by obtaining a major victory in the North, Lee and Davis hoped to draw attention to their cause from external sources. More specifically, the French were close to lending support for the Confederates, and a major victory in the North may well have been enough to encourage the French to throw their gauntlet into the ring. If that had happened, then the French navy would have been able to help relieve the blockades that had been set up by the Northern navy. This in turn would have allowed the Confederates to start receiving supplies from other sources.
The South had reached a point where they recognized that their chances were rapidly diminishing. After losing at Gettysburg, their fate was sealed and it became just a matter of time before the inevitable happened. From that point on, they were mostly hoping to outlast the North. They didn't have the resources or manpower to launch any more offensives, so they could only hope that time would allow them to persuade other foreign powers to come to their aid.
I had some assistance from this source, but most of my answer is based on extensive reading on the American Civil War.
In June 1864, as General (later President) Ulysses S. Grant was leading the Army of the Potomac against Richmond, Lee DID order an offensive by one of his better remaining subordinates, General Jubal Early.
Early debouched from the Shenandoah Valley, cut a swath across Maryland and southern Pennsylvania, and threatened Washington.
But the South had few punches left after Gettysburg. They had reached their "high water mark" there, losing over 20,000 men, including several generals killed or wounded to no purpose. This, after the loss of 13,000, including that of General "Stonewall Jackson, at the previous battle of Chancellorsville.
The day after Gettysburg, General Ulysses S. Grant had captured Vicksburg, Mississippi, establishing Union control of the whole Mississippi river, cutting off Texas, Louisiana and Arkansas, plus the re-occupied states of Mississippi and Tennessee from the Confederacy. In effect, the latter was now fighting with only six states out of eleven.
These victories soon led to the promotion of Grant to the de facto commander Army of the Potomac, who allowed the Confederates few openings to counter invade the north. The previous invasions had followed Union defeats at the Second Battle of Bull Run (ending at Antietam), and the battle of Chancellorsville, prior to Gettysburg.