Data breach is an event where your personal information is been stolen by an attacker. For example your account summary statement or even family vacation pictures you have taken. The data that is been stolen depends on its value, will be sold in the dark web market, or release freely to the market. It is almost impossible to determine whether you have been a victim of data breach unless it is being publicize or viral in social media.
If you are a victim of data breach, most of your online accounts may have been compromised. This includes your email account which nowadays a must priority to exist online. Some of the evil things that an attacker can do with your email is to send out phishing emails which harvest credential of other users. Other that they can also use it to impersonate you and call all sorts of trouble.
So what is your action?
First of all if you are unsure if your email has been compromise or not, you can visit data breach email checker to identify whether your account have been breach.
If your email had been compromised what would you do?
Change all your online account credential including online banking, email and social media just to be sure that it is secured.
Last but least, always be vigilant whenever you are online. Make it a habit to always browse to safe websites and clear you browser cache, cookies and history.