The steel a knife is made from quietly decides almost everything about how it performs: how sharp it gets, how long it stays sharp, and how much care it needs. You do not need a metallurgy degree, just a grasp of a few trade-offs.
Hardness is the key dial Steel hardness is measured on the Rockwell scale (HRC). Softer steels (around 54 to 58 HRC), common in German knives, are tougher and forgiving. They resist chipping, survive abuse, and re-sharpen easily, but the edge dulls faster. Harder steels (around 60 to 64 HRC), common in Japanese knives, take a finer, keener edge and hold it much longer, but they are more brittle and can chip if you twist them or hit bone.
German vs Japanese, simplified - German (e.g. Wusthof, Victorinox): softer steel, thicker blade, curved belly, rugged and low-maintenance. A great everyday workhorse. - Japanese (e.g. Mac, Tojiro): harder steel, thinner blade, flatter profile, scary sharp and precise, but demands gentler handling.
Neither is better; they suit different cooks. A busy household that is hard on tools may prefer German. A careful cook who loves a keen edge will adore Japanese steel.