Module -> localize names of variables (lexical scoping)
Block  -> localize values of variables (dynamic scoping)
Module creates new symbols:
Module[{x}, Print[x];
 Module[{x}, Print[x]]
]
->x$119
->x$120
Block localizes values only; it does not create new symbols:
x = 7;
Block[{x=0}, Print[x]]
Print[x]
->0
->7