Pokémon card rarity guide
Every Pokémon card has a rarity symbol in the bottom corner. Here is what each one means and which rarities collectors chase.
The basic symbols

A circle means common, a diamond means uncommon and a black star means rare. Older sets added holo rares (with a foil picture) on top of these.
Modern rarities

Recent sets mark rarity with stars: two black stars for a double rare, then ultra rares, and gold stars for the chase cards. One gold star is an illustration rare, two is a special illustration rare, and three is a hyper rare, the gold cards.
Illustration rares show the Pokémon in a full scene drawn by one artist; special illustration rares are the biggest chase cards in most modern sets.
Secret rares and amazing rares

A secret rare is numbered above the set's official count (for example 201/198). Gold cards, rainbow rares and many full arts are secret rares.
Amazing rares, from the Sword & Shield era, have a rainbow background that spills over the card frame.
Rarity isn't the whole price
The Pokémon on the card matters as much as its rarity: a Charizard, Pikachu or Umbreon illustration rare usually sells for much more than another Pokémon's card of the same rarity. Condition and grade then decide the rest.
See also: most valuable Pokémon cards · Crown Zenith price guide · Hidden Fates price guide