Short answers, pulled from the story.
Omaha Beach was a 5-mile section of the Normandy coastline running from west of Sainte-Honorine-des-Pertes to east of Vierville-sur-Mer. It was chosen because it was the only way to link the British landing at Gold to the east with the American landing at Utah to the west, forming a continuous Allied beachhead along the Normandy coast.
American forces suffered 2,400 casualties at Omaha Beach on the 6th of June 1944. Total V Corps casualties, including killed, wounded, and missing, are estimated at between 5,000 and over 6,000, depending on the source. By the end of the day, 34,000 troops had been landed despite those losses.
Omaha Beach was defended by the German 352nd Infantry Division, which Allied intelligence had not expected to be present. Four lines of obstacles in the tidal zone, fifteen fortified strongpoints above the beach, and only five narrow draws as vehicle exits concentrated fire on every approach. The Allied air and naval bombardment that preceded the landing produced almost no damage to those defenses.
The 352nd Infantry Division, with 12,020 men including 6,800 experienced combat troops, was the main German force defending Omaha Beach on the 6th of June 1944. Field Marshal Rommel had ordered it forward from near Saint-Lo to the Normandy coast in March 1944. Allied intelligence learned of the relocation by June 4 but made no changes to the assault plan.
Colonel George Taylor of the 16th RCT landed at 08:15 and rallied pinned troops with the order: "Two kinds of people are staying on this beach, the dead and those who are going to die." Brig. Gen. Norman "Dutch" Cota of the 29th Division led the first successful breach of the wire at Dog White using a Bangalore torpedo. Task Force O, the naval component responsible for the landing, was commanded by Rear Admiral John L. Hall Jr.
Mulberry A was a prefabricated artificial harbor assembled offshore at Omaha Beach, with construction beginning the day after D-Day. It became operational by D+10, when LST 342 docked and unloaded 78 vehicles in 38 minutes. A storm that struck three days later, raging until the night of June 22, destroyed the harbor before it could be repaired; in its brief operation, 11,000 troops, 2,000 vehicles, and 9,000 tons of equipment came ashore through it.