Explain xpath OR conditions.

XPath OR definitely supports OR expressions. It is also case-sensitive. Use text() rather than TEXT() and or rather than OR. You didn't show us the HTML fragment, so I can't tell whether you really want 'USER NAME' or 'user name' or 'User name'. You will have to figure that out for yourself.

Try this:

   //div[text()='USER NAME' or text()='USER ID']

When you run into problems like this, go to the web page you are interested in and open up the browser debugger. You can probably experiment with XPath expressions there. In the Chrome debugger, you can use

$x(expression goes here),
e.g.
$x("//div[text()='USER NAME' or text()='USER ID']"