>>42487200Rock includes creatures with a mineral outer layer. A snail with Rock-hard shell or an animated rock-golem.
Ground is a balancing type inserted at later stages of the development. It mainly described buff, sturdy, thick-skinned Normal types, like crocodiles and rhinos. These creatures are large enough to endure poison and thick enough to resist electricicty. A sort of antithesis to the frail Flying type.
The weaknesses of this type make more sense for an exclusive serpent-type. Its Gen1 attacks reflect that it is simply a specialised Normal type(with dig and earthquake).
In a hopeless attempt to legitimise the type, they also inserted the underground theme for its creatures and mud&sand themes for its attacks(but they have always been creatively bankrupt, see Earth Power).
Nowadays, GFreak is desperate for variety in creature-design and to maintain its VGC fanbase. Thus, it attempts to evolve types into something almost nonsensical. Ground now is also a clay type. Dragon attacks are just lasers and slashes. Grass attacks are just laser balls and powders etc..
