Drag and drop the number from the right to the number on the left so they both add up to the number in the selection box.
In other words: Click and hold the button down while moving the number. Release the button when over the other number.
There is also a Number Bonds To 10 version of this game here.
The resources listed below are aligned to the same standard, (2NBT05) re: Common Core Standards For Mathematics as the Addition and subtraction game shown above.
Fluently add and subtract within 100 using strategies based on place value, properties of operations, and/or the relationship between addition and subtraction.
Similar to the above listing, the resources below are aligned to related standards in the Common Core For Mathematics that together support the following learning outcome:
Use place value understanding and properties of operations to add and subtract