When programming for touch, you will likely use the Touch APIs / events offered by the development framework of choice, and that framework will interface with whatever touch interface is available within the operating system.
Writing a touch application for an OS that supports touch will likely be satisfied with the standard touch interface built into the development tool/framework.
However, there are times when you may wish to utilise a different interface / API, for example to write a touch enabled cross-platform application.
These articles introduce you to the UPDD driver API and offer some insight on ways you might utilise touch within cross-platform applications and multitouch considerations.