Mahjongg solitaire is a tile matching game played with one person.
There are many different variants, but the basic premise is usually the same. To play you select a tile, stone or whatever you call it, then its match. Doing so removes the two tiles, possibly revealing more tiles underneath. The goal is to clear the board, that is remove all the tiles.
Some games have a timer. The timer might count up, or the timer might count down. Some timers count from tile to tile, other for the entire game. Some timers are related to bonus points.
While we are on the subject of points. Most games keep some sort of score. Sometimes based on speed, sometimes tile have different point values. Keeping score can be fun, so you can measure your improvement. Try to beat your last score, and get better each time you play.