The tarot cards have many layouts, called spreads, which vary from simple to very complex. As may be surmised, the more simple spreads utilize only the Major Arcana, the most complex use the entire 78 card deck.
Learning how to read tarot cards requires gaining a thorough knowledge of what each card represents. The process is complicated by the fact that the orientation of the cards affects meaning (for example an upside-down card in a spread means that the original meaning of the card is reversed) as does the placement next to another card in the divination spread. Cards are said to influence each other in the latter instance.
Tarot cards are enjoying great popularity in the modern age, a search engine query of tarot cards for sale will reveal hundreds of different decks. While the structure remains loosely the same as the traditional card sets (Ride-Waite), the theme of the cards as represented in the artwork on the cards can vary widely. Theme tarot decks may feature particular animals (cats); or a style of art (a popular recent deck is “steampunk”, a sci-fi blend of historical and modern technology); a geographic location (a Russian themed deck with beautiful art inspired by St. Petersburg) and many dozens of others.
Theme decks also often feature the work of one particular artist; some are so beautiful that they are collected as art and not as divination tools.
via Jean Pierre’s Tarot Reading (click to read more)