What is the difference between Solitaire and Spider Solitaire?

While both share the Solitaire name, Klondike and Spider are quite different games. Klondike Solitaire uses one 52-card deck dealt into 7 tableau columns. You build foundations up by suit from Ace to King, and arrange tableau columns in descending order with alternating colors. Draw from the stock pile when stuck. Most hands are winnable with good strategy and some luck. Spider Solitaire uses two 104-card decks dealt into 10 tableau columns. There are no foundation piles — instead, you build descending sequences of the same suit within the tableau. Complete a King-to-Ace sequence of the same suit to remove it. You can deal additional rows from the stock when stuck. Spider is significantly harder than Klondike. In 1-suit Spider (easiest), most games are winnable. In 2-suit Spider, roughly half of games are winnable with perfect play. In 4-suit Spider (hardest), very few games can be won. Which to choose: Klondike for relaxing, accessible play. Spider for a more challenging, strategic experience. Both develop planning, patience, and spatial reasoning.