Macro conversion is the main conversion on a website. Macro conversions are primary. Macro means big, on a large scale. Macro conversions show the website's Conversion Rate's which is quite important for a brand or a service.
For example, selling a product or receiving a service request are macro. Micro Conversions may often promote to macro conversions. That's why you should track micro conversations.
There are fewer macro conversions than micro conversions because macros mostly exists at the end of the sales funnel. If you get a macro conversion, this means that you successfully achieved your goal for that particular customer.