$ContextPath is a global variable that gives a list of contexts, after $Context, to search in trying to find a symbol that has been entered.
Each context is specified by a string of the form "name`".
The elements of $ContextPath are tested in order to try and find a context containing a particular symbol.
$ContextPath is modified by Begin, BeginPackage, End and EndPackage.
$ContextPath is a rough analog for Mathematica symbols of the "search path" for files in many operating systems.
See Section 2.7.8.
New in Version 1.