Of course there are many more, but like the above they are all pretty simple.
However, as mentioned XMLs tags and elements are made up by the user. Due to this it can lack structure and may be hard to find software that translates the code into the format that one wishes. Content models such as DocBook help with this. DocBook is a collection of standards and tools for technical publishing, originally created by software companies as a standard for computer documentation, it can now be used for other kinds of content and has been adapted for many purposes. DocBook provides a number of tags that allow the user to easily publish the documents in any other form of documentation such as PDF and HTML. Other content models include: DITA (Darwin Information Typing Architecture), S1000D, XBRL and more.
All in all, XML may seem a bit complex to understand, but it is being used in many different areas for its simplicity. It chooses brains over beauty, focusing more on the logical information, rather than how it is formatted. Therefore, it is used in various different professions and industries. Including, finance, publishing, medicine, science and many more.