Just a quick explanation: You're probably using the same password with different websites and accounts. Some websites have very bad security when it comes to passwords and personal information. Thus, when a data breach or database hack occurs in one of these websites, pretty much ANYONE with enough motivation can get that info for their own use. As an example: You create an account for a new mobile game/game website/social media/etc.. As the average internet user, you cannot be bothered to remember multiple, different passwords, so you use the SAME password that you use pretty much everywhere. Of course, your newly made account also has certain personal information that you had to include (Maybe your birthday, oftentimes your full name, or you just have a VERY unique in-game name that people can search and trace back to you). Now this new mobile game/game website/social media/etc. you have your new account in experiences a data breach (An employee stole and sold the customer data, a virus/hacker virtually steals the info due to bad security, etc.). Now your personal info is out there. Oh don't worry, they only have everything you input for the account. As long as you didn't use the EXACT SAME PASSWORD on ANY OTHER ACCOUNT IN OTHER WEBSITES you are mostly safe.

tl;dr Don't use the same password for every account, and stop creating accounts in shady/mediocre/untrustworthy websites.