Almost every serious account compromise traces back to the same root cause: password reuse. One website you signed up to years ago gets breached, the attackers take the leaked email-and-password list, and they try that same combination on your email, your bank and your shopping accounts. Because most people reuse a handful of passwords, it works far too often.
A password manager exists to end that problem completely. It generates a long, random, unique password for every account, stores them all in an encrypted vault, and fills them in for you — so the only thing you ever have to remember is one strong master password.
Why a vault beats your memory
Human memory forces a trade-off: passwords you can remember are weak, and passwords that are strong you cannot remember. A password manager removes the trade-off. Each site gets a genuinely random 16-plus character password that no human would ever memorise, and you never need to — the manager remembers for you and types it in on the right site.
That "right site" part is a hidden security bonus: a good manager only offers to fill a password on the exact domain it was saved for, so it quietly refuses to hand your bank password to a look-alike phishing page. Your memory has no such safeguard.
Is it safe to put everything in one place?
The common worry is that one vault is a single point of failure. In practice the vault is encrypted so that even the provider cannot read it without your master password, and reputable managers are built so that decryption happens only on your device. The realistic risk of forgetting a hundred unique passwords is far larger than the risk of a well-designed vault.
You do need to protect the master password well — make it a long passphrase you have never used elsewhere — and turn on two-factor authentication for the vault itself. With those two steps, a manager is dramatically safer than the reuse-everything habit it replaces.
How to switch without pain
Do not try to fix every account in one sitting. Install a manager, set a strong master passphrase, and let it save logins as you use sites normally over the next weeks. Each time you log in somewhere, let the manager generate a new unique password for that account and update it. Start with the accounts that matter most: email first (because it can reset everything else), then banking and finances.
Within a month of normal browsing, your most important accounts will each have a unique, strong password, and the old reused password will be retired. It is one of the highest-return security moves available, and it costs almost nothing but the decision to start.