How do you get rid of the buttons?

Buttons are a multi stage obstacle to clear which means you need to match next to them several times to clear one. Each button will have a number of threads on them and may also have a colour circle, each of these is a stage to clear.

Once all the threads are gone the button will clear. If it is joined by string threads to other buttons in a line then these will also clear at the same time. So you can concentrate on hitting one button in a thread to remove them all.