If you are not familiar with the notion of hardware wallets, you may wonder what would be the advantages versus a paper wallet or an encrypted private key on a computer.
The main principle behind hardware wallets is to provide a full isolation between the cryptographic secrets (private keys) and your easy to hack computer or smartphone. Vulnerabilities of modern PCs and smartphones are well known, and if you keep your private keys there (private key = your bitcoins) it’s just a matter of time before you’ll get hacked and lose everything.
A paper wallet may be secure, but only until you want to use your funds, requiring importing your private keys on your computer. And if you think a password encrypting your keys is enough, malware is smart enough to wait for the inevitable decryption before sweeping your funds.
Hardware wallets are convenient, affordable, portable and backed-up by a paper wallet allowing an easy recovery in case of loss. If you have any significant amount of bitcoins, using a hardware wallet should be a no-brainer.