You can do a search for the variable name and find out where the data comes from and what it is being used for. If the variable name is not helpful, perhaps the name of the XML tag it is loaded from (assuming it is loaded and not generated some other way) will help. But in general the name of a variable does not really have anything to do with what it is used for - the computer doesn't care what you call it, only what you do with it. Therefore the only way to really know what it is for is to do that search and look at everything it is used for.
For example, say the InfoThing class has a variable m_iData. This is probably not a useful name, all variables hold data so it tells you pretty much nothing other than the "i" probably means it is an integer but you can tell that by how it is declared anyway. So you search for m_iData, focusing initially on the file where InfoThing is declared. It probably has an InfoThing::getData function that returns the value of m_iData and also an InfoThing::setData function that sets it, and maybe an InfoThing::changeData function as well. (The variable might not appear anywhere else other than perhaps the initialization code for InfoThing.) So search for setData and see where it is being called. If the variable is loaded from some data in an XML file then the XML parsing code for InfoThing must set it, so what tag in what XML file is the source? If it is not loaded, it must be used to hold some value that is somehow calculated from other things. What are those things? After seeing where the data in that variable comes from, you'd check to see where getData is called to see how it is being used.