send_email_on_row_change (Click on Extensions > Apps Script.)

send_email_row.js

function onEdit(e) {
    // Get the range that was edited
    var range = e.range;
    var sheet = range.getSheet();
    // Specify the column that triggers the email (e.g., column 3 is column C)
    var triggerColumn = 3;
    // Check if the edited column is the one we are interested in
    if (range.getColumn() == triggerColumn) {
        // Get the row of the edited cell
        var row = range.getRow();
        // Get the email address from a specific column (e.g., column 1 is column A)
        var emailColumn = 1;
        var emailAddress = sheet.getRange(row, emailColumn).getValue();
        // Get the subject and body of the email
        var subject = "Google Sheet Update Notification";
        var body = "The value in column " + String.fromCharCode(64 + triggerColumn) + " has been changed to: " + range.getValue();
        // Send the email
        if (emailAddress) {
            MailApp.sendEmail(emailAddress, subject, body);
        }
    }
}