The two are separate topics, I just happen to put them in the same post for now. Closure Closure is the capability to remember it's lexical scope, even when executed outside it's lexical scope. If two inner functions, are within the same scope, they share the same closure. Lexical scope The lexical scope is the scope in which a variable is declared during the first pass of the javascript compilation, which has two passes, compilation and execution. During the compilation pass, the compiler goes through the code looking for formal declaration, that is, var, function and parameters of function. For each of these formal declarations, the compiler will check the current lexical scope, and add this identifier if it isn't already there. Then at the second pass, execution, the compiler will run the code as we are intuitively use to and once it reaches the the identifiers found earlier, will ask if they are left hand side(RHS), or right hand side (LHS). If th...