This game from Online Solitaire is considered to be the classic solitaire game. It's the game that you played on your Windows computer as a kid and have been improved in this version for the web.
It contains all the features you know and love from Windows solitaire, along with many improvements. It features unlimited free games and daily challenges. If you're stuck, you can get helpful hints, and you can undo your moves all the way back to the beginning of the game.
The rules are simple. The game is played with a standard deck containing 52 cards. The game consists of 7 piles, a foundation, the stock and the waste. When you begin a new game, see if you can move a card from one pile to another. A card can be moved if it's one value below and another color than the card it's being moved onto. Cards are moved to the foundation in descending order, starting with the ace. When all cards are on the foundations, the game is won! If the rules still seem a bit confusing, you can look through this guide on how to play solitaire, which contains illustrations and an explainer video.