Scoping Constructs

Begin — temporarily set the current context
BeginPackage — temporarily set the context and clean the context path
Block — evaluate an expression using local values for some given symbols
System`Private`$ContextPathStack — internal variable tracking $ContextPath values
$ContextPath — the current context search path
System`Private`$ContextStack — internal variable tracking $Context values
$Context — the current context
Contexts — list defined contexts
End — revert to the context previous to the nearest 'Begin' statement
EndPackage — restore the context and the context path to the state before the nearest call to 'BeginPackage'
Module — generates symbols with names of the form x$nnn to represent each local variable.
$ModuleNumber — serial number of the current local module
Unique — generate a new symbols with a unique name
With — replace variables by some constant values