In one sentence: A data breach is when information that a company or organization holds is seen, taken or shared by people who should not have it.
Why it matters: Breaches can happen by hacking, by mistake or by a lost device. If a company tells you that your details were in a breach, it does not mean you were hacked.
One thing to do: If you get a breach notice, first check it is real by going to the company website yourself. Then change the password for that account and for any account where you used the same one.
Related terms: credential stuffing, identity theft, dark web
Learn more: What Is a Password Manager, and How Do You Choose One?; How to Secure Your Email Account (It Unlocks Everything Else)
Checked: 25 Oct 2026. Settings screens change. If yours looks different, search the company's help page.
