What is a locator? Name the different types of locators in Selenium?

A locator is an address that uniquely identifies a web element within a web page. Selenium has several different types of locators to identify web elements in web pages. These include: 

1. ID
2. Name
3. ClassName
4. TagName
5. LinkText
6. PartialLinkText
7. XPath
8. CSS Selector
9. DOM