Here's a typical progression:
Acquisition: The thief obtains your personal information (Social Security number, credit card details, etc.) via data breaches, phishing scams, etc.
Exploitation: The thief uses your information to open fraudulent accounts, make purchases, or file fake tax returns.
Discovery: You notice the fraud through suspicious credit activity, bills, or declined transactions.
Resolution: The long arduous process of disputing charges, working with credit bureaus, and potentially law enforcement.