What does the term "Meta" stand for in reference to Meta Data within SharePoint 13?
Meta-Data:- It means data about data. Or more precisely more information about some 'information '.
In context of SharePoint (whether it's 2013) , in general it is information attached to elements. The different type of values entered for an element in a list or library. First we have columns and values present under the columns is known as "Metadata".
Say a document with name "HrLeavePolicy" is saved with column values such as
Column1 : Purpose
Value : "Leave"
Column2 : Department
Value : "IT"
Now document "HrLeavePolicy" is tagged with metadata 'Leave' and 'IT'.
This metdata is very useful as later users can possibly search the document using metadata 'Leave' and 'IT'.