: If a user reuses the same password across multiple sites, a leak from one service can grant an attacker access to their email, banking, or other streaming accounts.

: Use a tool like Have I Been Pwned to see if your email address has appeared in known data breaches.

: Services like Bitwarden or 1Password can generate and store unique passwords for you, making it impossible for one leak to compromise all your accounts.

Confirms it is a list of credentials (usually email:password ).

The name strongly suggests a combolist , a type of database file used by cybercriminals for "credential stuffing" attacks.