Short answers, pulled from the story.
Joseph E. Johnston was one of the Confederacy's most senior generals, holding the rank of full general. He commanded at the First Battle of Bull Run in July 1861, defended Richmond during the 1862 Peninsula Campaign, and led the Army of Tennessee during Sherman's Atlanta campaign in 1864.
The feud centered on Johnston's belief that he deserved to be ranked first among Confederate full generals, since he was the highest-ranking U.S. Army officer to resign and join the Confederacy. Davis backdated Johnston's promotion to the 4th of July 1861, placing Johnston behind Samuel Cooper, Albert Sidney Johnston, and Robert E. Lee. Johnston sent Davis an angry letter that Davis found intemperate enough to discuss with his cabinet, and the conflict widened with each subsequent campaign.
At Bennett Place, a farm near present-day Durham, North Carolina, Johnston surrendered the Army of Tennessee and all remaining Confederate forces in North Carolina, South Carolina, Georgia, and Florida on the 26th of April, 1865. The surrender totaled 89,270 soldiers, making it the largest surrender of the Civil War, larger even than Lee's surrender at Appomattox.
President Davis removed Johnston on the 17th of July, 1864, after Johnston's army had ceded more than 110 miles of territory in two months without a decisive engagement. Davis sent Gen. Bragg to Atlanta to assess the situation, and Bragg recommended Johnston's removal. Johnston's replacement, Lt. Gen. John Bell Hood, was forced to abandon Atlanta by September.
Both generals praised Johnston in their memoirs. Sherman called him a "dangerous and wily opponent." Grant wrote that Johnston's tactics in the Atlanta campaign were correct, arguing that prolonging the war further might have exhausted the North enough to force a settlement. Grant also supported Johnston's decisions during the Vicksburg campaign, saying an assault on Union forces would simply have inflicted losses on both sides without result.
Johnston died of pneumonia on the 21st of March, 1891, in Washington, D.C., one month after serving as an honorary pallbearer at Sherman's funeral. During the funeral procession in New York City on the 19th of February, 1891, Johnston stood bareheaded in cold, rainy weather as a sign of respect for Sherman, and the cold he caught that day developed into the pneumonia that killed him.