มีคำถามเกี่ยวกับ openDatabase(); ใช้งานยังไงแล้วมันเก็บค่าไว้ที่ไหนยังไง

 var results = document.getElementById('results'); 
 var id = document.getElementById('id');
 var firstName = document.getElementById('firstName');  
 var lastName = document.getElementById('lastName');  
 var phone = document.getElementById('phone');
   
 var createStatement = "CREATE TABLE IF NOT EXISTS Contacts (id INTEGER PRIMARY KEY AUTOINCREMENT, firstName TEXT, lastName TEXT, phone TEXT)";
 var selectAllStatement = "SELECT * FROM Contacts";
 var insertStatement = "INSERT INTO Contacts (firstName, lastName, phone) VALUES (?, ?, ?)";
 var updateStatement = "UPDATE Contacts SET firstName = ?, lastName = ?, phone = ? WHERE id = ?";
 var deleteStatement = "DELETE FROM Contacts WHERE id=?";
 var dropStatement = "DROP TABLE Contacts";

 var db = openDatabase("AddressBook", "1.0", "Address Book", 200000);
 var dataset;
 createTable();

      function onError(tx, error) {
        alert(error.message);
      }
      
      function showRecords() {
        results.innerHTML = '';
        db.transaction(function(tx) {
          tx.executeSql(selectAllStatement, [], function(tx, result) {
dataset = result.rows;
            for (var i = 0, item = null; i < dataset.length; i++) {
              item = dataset.item(i);
              results.innerHTML += 
                  '<li>' + item['lastName'] + ' , ' + item['firstName'] + ' <a href="#" onclick="loadRecord('+i+')">edit</a>  ' +  
 '<a href="#" onclick="deleteRecord('+item['id']+')">delete</a></li>';
}
          });
        });
      }
      
      function createTable() { 
        db.transaction(function(tx) {
          tx.executeSql(createStatement, [], showRecords, onError);
        });
      }
      
      function insertRecord() {
        db.transaction(function(tx) {
          tx.executeSql(insertStatement, [firstName.value, lastName.value, phone.value], loadAndReset, onError);
        });
      }
      
 function loadRecord(i) {
var item = dataset.item(i); 
        firstName.value = item['firstName'];
lastName.value = item['lastName'];
phone.value = item['phone'];
id.value = item['id']; 
      }

      function updateRecord() {
        db.transaction(function(tx) {
          tx.executeSql(updateStatement, [firstName.value, lastName.value, phone.value, id.value], loadAndReset, onError);
        }); 
      }
      
      function deleteRecord(id) {
        db.transaction(function(tx) {
          tx.executeSql(deleteStatement, [id], showRecords, onError);
        });
resetForm();
      }
       
      function dropTable() {
        db.transaction(function(tx) {
          tx.executeSql(dropStatement, [], showRecords, onError);
        });
resetForm();
      }

 function loadAndReset(){
 resetForm();
 showRecords();
 }

 function resetForm(){
firstName.value = '';
lastName.value = '';
phone.value = '';
id.value = ''; 
 }