Data Loss Prevention is an important topic for SMC and especially with Microsoft 365. We have a training course for this topic in Actuate which has more information, please take that course if you have questions about this topic.
Information that is being tagged include (but aren't limited to):
Credit Card Number
U.S. Bank Account Number
U.S. Individual Taxpayer Identification Number (ITIN)
U.S. Social Security Number (SSN)
U.S. Driver's License Number
Here some practical examples and highlights what happens when data is flagged by a policy and what you can do.