I am using RoboHelp for the first time. I am confused about what a user defined variable is and how it differs from a master page item (like those used in InDesign). Does the term "user" refer to the person creating content in RoboHelp or the person who will be accessing the content online?
One of the common things in a project is perhaps a Company Name. And if that company ever gets sold, the Company Name usually changes. So if you declare a variable, wherever you want the Company Name to appear in the files, you insert the variable instead. That way, if the name changes down the road, you just change the name in the variable and everywhere it has been used, it updates to reflect what the variable contains.
They are called "User Defined Variable" because the help author (the RoboHelp user) chooses what they are called, where they are used and what they contain.