If you wish to protect specific data in your company, you need to define their classifications first.
Data classifications allow you to define what data is considered sensitive in your company (e.g. personal information, credit card numbers, outputs of certain applications, etc.) and help you classify files into different groups based on who, where, and how can work with them. You can use data classifications in policies to detect and secure files that contain sensitive information.
In the Data classification section, you can see a list of classifications you set up and when they were last edited.
Data classifications are not prioritized, they are ordered alphabetically. Classifications are evaluated and protection is determined by linked protection policies and their priority.