Phantom wallet with hardware

@witebutr has provided more than enough info to your question. To add to the info already provided. Security is the main reason you need to connect your hardware wallet to phantom because your keys don't leave your wallet and, you also need to authenticate any transaction with your hardware wallet giving you an extra layer of security in an event where your phantom seed phrase is compromised.

Phantom Wallet supports connection to Ledger Wallet.  Ledger is a hardware wallet that has been around for quite some time and is one of the more well-known and trust hardware wallets.

Further, a hardware wallet is a separate device that you store your crypto on that is considered to be more secure than online wallets, desktop wallets and mobile wallets.  Not all hardware wallets are the same and not all hardware wallets partner with all sites or carry all cryptos.  

Phantom and Ledger have a partnership that allows the connection of the two.  So if you are looking for more secure storage system than Phantom Wallet alone, you should look into getting a Ledger Wallet.