It has milk where the regular macchiato has got only foam.
Because who wants the same cup of coffee every day? But if you get an extra shot of espresso, it ups the caffeine content and cuts the sweet a little.
Essentially, the difference between the familiar caffe latte and the latte macchiato is that the milk in a latte macchiato is supposed to be added before the espresso, which creates a mark of espresso in the milk foam.