Unix program used via command-line. See touchpad or touchscreen if your question relates to those instead.
touch is a standard Unix command that will work on any Unix-based system. It can be used to update or changes a file's (or directory's) time-stamp in regards to when it was last accessed and/or modified. It can also be used to create a new empty file.
Touch syntax is as follows:
touch [option] fileto update a file
touch fileto create a new file
For questions about tactile interfacing see either: