Scope
Applies to: general, python
Scope is the region of code where a name is visible. A variable defined inside a function is local to it and vanishes when it returns; names defined outside are broader. Scope keeps parts of a program from clobbering each other's variables.
x = 1 # module scope
def f():
y = 2 # local to f; invisible outside
return x + y # can read the outer x