As the article explains, there used to exist light tanks and heavy tanks until advancement of technology made the distinction obsolete and we ended up with only

As the article explains, there used to exist light tanks and heavy tanks until advancement of technology made the distinction obsolete and we ended up with only the "main battle" type of tank combining maneuverability, armor and firepower in a single package. As the article also explains, German "panzer" and English "tank" simply have different meanings, at least pedantically speaking. Translations aren’t always 1:1. (My native language actually follows the German convention.)