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, or implement multitouch support in cases where the OS does not natively support multitouch, such as macOS.
These articles introduce you to the UPDD driver API and other ways you might utilise touch within cross-platform applications, along with things to consider when adding multi-ouch.