Tarot cards are a tool for self-understanding using symbolic imagery and words and consisting of two parts – the Minor Arcana and the Major Arcana. 

The Minor Arcana is just like a deck of playing cards, with 4 suits and 14 cards per suit (ace through king). The Major Arcana usually includes 21 cards that are numbered Roman numerals I through XXI. 

These days, there are literally hundreds if not thousands of tarot decks available. Many artists and writers have made their own decks and there is a plethora to choose from. There are also different kinds of “oracle” decks that are not tarot decks. What makes it a tarot deck is the structure described here.