Short answers, pulled from the story.
The Second Battle of Bull Run was fought August 28-30, 1862, in Prince William County, Virginia. It was fought on the same ground as the First Battle of Bull Run, which had taken place on the 21st of July 1861.
Union Major General John Pope commanded the Army of Virginia, which grew to roughly 70,000 men during the battle. Confederate General Robert E. Lee commanded the Army of Northern Virginia, totaling approximately 55,000 men, with his force organized into two wings under Major General Stonewall Jackson and Major General James Longstreet.
On the 30th of August 1862, Longstreet launched a counterattack with 25,000 men in five divisions, described as the largest simultaneous mass assault of the entire Civil War. The attack crushed the Union left flank and drove Pope's army back across Bull Run toward Centreville.
Union casualties totaled approximately 14,462, including 1,747 killed, 8,452 wounded, and 4,263 captured or missing, out of about 70,000 engaged. Confederate casualties were approximately 7,387, including 1,096 killed and 6,202 wounded, out of about 55,000 engaged.
Fitz John Porter was arrested on the 25th of November 1862, and court-martialed for his actions on August 29. He was found guilty of disobedience and misconduct on the 10th of January 1863, and dismissed from the Army on January 21. A special commission under General John M. Schofield exonerated him in 1878, and President Chester A. Arthur reversed his sentence eight years later.
The Confederate victory emboldened Robert E. Lee to launch the Maryland campaign. On the 3rd of September 1862, the vanguard of the Army of Northern Virginia crossed the Potomac River, leading to the Battle of Antietam. Pope was relieved of command on September 12 and his army was merged into the Army of the Potomac under McClellan.