Touch is a command to update the date and time of a particular file(s) or directory (to the present date and time). This command will 'touch' all files and recursive files in the current and recursive directory (but not the directories themselves).
find . -type f -name "*.txt" -exec touch {} +
The . can be changed to a particular file name or directory name, and the f, which stands for 'file' can be changed to d for directories.