Use reputable services like Have I Been Pwned to see if your email has appeared in any known combolists or breaches.
Bots take the combolist and systematically try every pair on popular websites like Netflix, Amazon, or banking portals. 139k FR TARGET COMBOLIST.rar
Use a password manager to ensure every account has a unique, complex password. If one site is breached, the others remain safe. Use reputable services like Have I Been Pwned
Usually, they are simple text files containing thousands (or millions) of username:password or email:password pairs. the others remain safe. Usually