Short answers, pulled from the story.
MG 34 is short for Maschinengewehr 34, meaning machine gun 34 in German. It is a recoil-operated, air-cooled, general-purpose machine gun chambered for the 7.92x57mm Mauser rifle cartridge, and is generally considered the world's first general-purpose machine gun (GPMG).
The MG 34 was first tested in 1929, introduced in 1934, and issued to units in 1936. It was based on a 1930 Rheinmetall design under the direction of Louis Stange at Rheinmetall's Sommerda office, with Heinrich Vollmer of Mauser Industries adapting the design and redesigning the feed mechanism.
Einheitsmaschinengewehr means universal machine gun in German. The concept required a single weapon that could be transformed for multiple roles, including light infantry support, medium machine gun fire, anti-aircraft coverage, and sniping, by changing its mount, sights, and feed mechanism rather than fielding separate specialized weapons.
The MG 34's precision-milled components, tight tolerances, and high-quality metal alloys made it too complex and expensive for mass production. The MG 42 was developed using simpler mass-production techniques and surpassed MG 34 production in 1943. Germany nonetheless continued producing the MG 34 in parallel until 1945, with total wartime output exceeding 350,000 units.
The MG 34 could fire at a cyclic rate of up to 900 rounds per minute. In practice, accounting for reloading, aiming, and barrel changes, its effective rate of fire in combat was approximately 150 rounds per minute. US military tests under battle conditions found 7-10 round bursts, with 15 bursts per minute, to be most effective.
The MG 34 remained in service long after the war ended. Norway converted examples to .30-06 Springfield in the 1950s (MG34F1) and later to 7.62x51mm NATO (MG34F2), with the Heimevernet using them until the mid-1990s. At least one user entry records the weapon still in use in 2023.