Actually, the concept and adoption of the modern Main Battle Tank didn't come into being until after WW2 - during the war, the Sherman and T-34 were one of many types of tanks fielded.

There were tanks classified as heavy tanks - like the Soviet IS-2 and US M26 Pershing. These were designed to have equal or greater firepower and armor than tanks of lighter classes. However, they usually sacrificed mobility for this.

Then there were light tanks - like the M3 Stuart - which were designed primarily for reconnaissance roles and for fighting where heavier tanks were not available.

And its debatable to classify them as tanks, but nations also fielded a wide variety of tank destroyers and other armored vehicles designed to fight tanks or to provide armored assault options.