The Base Set was the very first card set released by Wizards of the coast in [199?]. It introduced a bunch of the original Pokemon as cards you could battle with.
Few people know of the "shadowless" cards. Even fewer people understand these cards. During the first run of this set, it was proposed that the cards be printed "as is" when the "1st Edition" stamp was placed. When the time came around to print the unlimited set, the cards looked worn and faded. You can tell if a card is "shadowless" by looking at the outer bottom right corner of the Pokemon's portrait. Many people think these cards are fake. 1st Edition base set cards with a shadow ARE fake cards. The only exception has been the Machamp that came with the starter set. That card will ALWAYS be 1st Edition.