How to handle errors and exceptions in Solidity?

In Solidity, errors and exceptions are handled using the 'require' function and the 'revert' function.

The 'require' function is used to check for a condition and throw an exception if the condition is not met. It can be used to enforce preconditions and postconditions on function arguments and return values. For example:

function divide(uint x, uint y) public returns (uint) {
  require(y > 0, "Division by zero");  // throw an exception if y is zero
  return x / y;
}

The 'revert' function is used to revert the state of the contract to the state it was in prior to the current call, and it can also be used to throw an exception with an optional message. It is typically used to revert the state of the contract when an error or exception occurs. For example:

function addFunds(uint amount) public {
  require(amount > 0, "Invalid amount");
  if (!msg.sender.send(amount)) {  // send the funds
    revert("Error sending funds");  // revert the state of the contract if the send fails
  }
}

Both the 'require' function and the 'revert' function will cause the current function to throw an exception and revert the state of the contract. If the exception is not caught and handled, it will propagate up the call stack until it is caught by the calling contract or client.