General meaning of micro means very small and macro means bigger.
In Scientific measurements, the micro is that size, which can be difficult to see with blank eyes and macro is size of object which can see with blank eye. For example we know that microscope is the instrument to view the objects, like molecules, bacteria, virus etc., which can not be visual to blank eye.
In mathematics, the micro and macro is compared with some standard unit. for example 1 meter is standard unit of mass in SI system then,
One micro meter = 1/100000 meter or 10^-6 meter.
But there is no measurable quantity like macro-meter, larger quantities than the unit are measured are, kilo meter 1000 times of meter, mega meter is 10^6 times of meter etc.
This is not only applied to the lengths but for all physical quantities like mass, time, pressure, force, energy, power etc.