A wallet address is a string of 26 to 62 characters that nobody can read back correctly over the phone. Miss one character when typing it and the money is gone to an address nobody controls. A QR code removes the typing step entirely: the scanner gets the exact string, character for character. That's the whole value, and it's why hardware wallets, payment terminals and exchange kiosks all print codes instead of printing letters.
Bitcoin addresses come in four shapes you will actually see in the wild. Ones starting with 1 are the original format, still valid after fifteen years. Ones starting with 3 wrap a script and were the first way to do shared wallets. Anything with bc1q is SegWit, cheaper to spend from, and bc1p is Taproot, the newest standard. All four work everywhere today. This generator checks the real checksum inside each type, so an address with a typo gets rejected before it becomes a QR you can send money to by mistake.
Ethereum works differently: one address starting with 0x receives ETH, USDT, USDC and every other ERC-20 token. There is no separate address per token, which is exactly where transfers go wrong, because the sending side picks the network and a wrong pick puts the tokens on a chain your wallet never looks at. Mixed capital letters in an Ethereum address are a checksum, not style, and we verify it. When handing out a QR for a token deposit, say the network out loud; the code carries the address, never the network.