Remove all the numbers. Two numbers can be removed by clicking on them. The two must be next to each other, either horizontally or vertically. That includes the case where one is at the end of a row and the other is at the start of the next row. The numbers must be the same or their sum must be 10. When there are no more numbers that can be removed, the remaining numbers are copied to the end again to open up new pairs.
The game is also known as TenPair, Numberama, Take Ten, 10 Seeds or Digits.