Answer:
In terms of programming it would be the difference between perfecting the structure of individual lines of code or blocks of code to correct for syntax.
While a global revision would be the overall check to improve efficiency and layout to accommodate better understanding of the codes purpose.
Local Revision: finding out why a certain piece of code handles certain throughput differently to normal data.
Global Revision: Cleaning out redundant code to make the program smaller or faster. Changing loops to fixed iterations to improve speed at the cost of file size. Adding features?