Short answers, pulled from the story.
The Vistula-Oder offensive was a Red Army operation launched on the 12th of January 1945 on the Eastern Front. Two Soviet fronts under Marshals Georgy Zhukov and Ivan Konev advanced over 300 miles from the Vistula River to the Oder River in just over two weeks, capturing Warsaw, Krakow, and Poznan and breaking the back of German Army Group A.
Marshal Georgy Zhukov commanded the 1st Belorussian Front and Marshal Ivan Konev commanded the 1st Ukrainian Front. Together they led 163 divisions totaling more than 2,200,000 infantry, 4,529 tanks, and 5,000 aircraft.
Zhukov halted the advance because of continued German resistance on his northern flank in Pomerania and a German counter-attack known as Operation Solstice against his spearheads. Soviet command decided to clear Pomerania first in the East Pomeranian offensive before launching the final drive on Berlin, which began on the 16th of April 1945.
Auschwitz was liberated on the 27th of January 1945 by the 322nd Rifle Division of the 60th Army, part of Konev's 1st Ukrainian Front. Despite SS attempts to destroy parts of the camp before retreating, Soviet forces found extensive evidence of the Holocaust.
Army Group A fielded roughly 450,000 soldiers against over 2,200,000 Soviet troops, a ratio of approximately five to one overall. Intelligence compiled by General Reinhard Gehlen estimated Soviet superiority at 11:1 in infantry, 7:1 in tanks, and 20:1 in artillery and aircraft, figures Hitler dismissed as a bluff.
As Soviet forces advanced west in January 1945, the SS began forcing concentration camp prisoners from Poland, East Prussia, Silesia, and Pomerania on foot marches toward Germany and Austria. The marches took place over hundreds of kilometers in sub-zero conditions without food or medicine. Estimates indicate that at least 250,000 men and women were marched in March and April 1945 alone.