What is the purpose of the doctype command?

Related questions

1. What is XML and why do we use it?
2. What is the advantage of XML?
3. For what XML is used?
4. What is Whatwg URL?
5. How is HTML different from XML?
6. What is .xml used for?
7. How is XML related to HTML?
8. What is doctype used for?
9. What is the need of XML?

Tags

1. #standards
2. #element
3. #being
4. #itself
5. #doctype
6. #while
7. #document
8. #declaration
9. #inform
10. #should
11. #visitor
12. #every
13. #rendered
14. #website
15. #browser
16. #compliant
17. #actually