How the transaction can happen without signing the transaction here?

Question

Why we can complete the transaction without signing it?

//sending transaction.
// Q: Why we don't need to sign transactions here?
const trxHash = await web3.eth.sendTransaction({
  from: accounts[0],
  to: accounts[1],
  value: web3.utils.toWei("1", "ether"),
});

console.log(trxHash.transactionHash);