Klondike is the solitaire everyone means when they say solitaire — the one that shipped with Windows and taught a generation to drag cards with a mouse. Seven tableau columns, a stock pile to draw from, and four foundations to build up from ace to king in each suit.
The tableau builds downward in alternating colours: a red six goes on a black seven. Kings, and only kings, can move into an empty column. Everything else follows from those two rules, and the difficulty comes from the cards you can't see yet.
Build four foundation piles up in suit from ace to king. In the tableau, stack cards in descending order with alternating colours, move ordered runs together, and fill empty columns with kings only. Draw from the stock when stuck.
With perfect play and full knowledge of the deck, around 80% of deals are theoretically solvable. Playing normally — without seeing the face-down cards — most players win considerably less often than that.
Yes. Tap a card and then its destination, or drag it. It runs in the browser with nothing to install.