XML is for data. HTML is for presentation.
A comparison
| XML describes data. | HTML describes presentation. |
| XML is designed to be created, read and updated by software. | HTML is designed to be created, read and updated by people. |
| XML parsers are strict. | HTML parsers are forgiving. |
| XML tags are case sensitive. | HTML is not case sensitive. |
| XML end tags are required | Some HTML elements have no end tag. E.g. <br> |