What is XML and its characteristics?

Related questions

1. How are XML and HTML related?
2. Why was XML created?
3. How is XML used today?
4. Why is XML still used?
5. Why is XML needed?
6. What is the use of XML?
7. What is so good about XML?
8. Is XML used anymore?
9. Does REST API use XML?
10. What is XML Excel?

Tags

1. #derived
2. #markup
3. #specifying
4. #extensible
5. #generalized
6. #which
7. #organize
8. #rather
9. #standard
10. #identify
11. #advertisements
12. #display
13. #store
14. #language
15. #stands
16. #based