A device fingerprint is data that was gathered about the hardware and software of computers, smartphones, and tablets. This data allows you to distinguish the user during an interaction with the web browser of said device.
Device fingerprints could include information such as:
location & time settings
Device fingerprint tracking enables you to use all this digital fingerprints to identify users across various devices such as desktop or mobile devices. It has been developed as an alternative to tracking via cookies as it works where cookies can’t.
More about the device fingerprint tracking on Piwik PRO blog: