Card graphics used to be dedicated graphics for each card, but have now been simplified to displaying the level or type in a common frame, so the only thing that is different for each card is the illustration
When Yasharn, Implacable Earth enters the battlefield, search your library for a basic Forest card and a basic Plains card, reveal those cards, put them into your hand, then shuffle your library
Suffice to say there are good reasons its such a hugely popular phenomenon, and one of them is the tactical depth and excitement of card by card play, with the advantage swinging from one player to the other until someone makes the final, fatal breakthrough
This ability counts creatures, not creature types
It was a massive, ongoing, mana-free source of card advantage that was played everywhere