Macro-linguistics and micro-linguistics are both fields of study of linguistics that focus on language and its form and meaning and the changes that occur to that form and meaning due to other factors; macro-linguistics examines language on a macro level, or from a more general perspective, while micro-linguistics examines language on a micro level, or in a more specific and particular way.
Macro-linguistics analyzes language beyond its most basic functions and context—it focuses on the social, cultural psychological, and neurological factors and how they're connected to the language and its structure. Thus, there are several subcategories of macro-linguistics, such as sociolinguistics (language and society), psycholinguistics (language and psychology), neurolinguistics (language and neurology), computational linguistics (language and IT), and others.
Unlike macro-linguistics, micro-linguistics studies language and its properties, structure, and functions specifically; thus, syntax (the structure of sentences), morphology (the structure of words), phonology (the study of sounds and speech), semantics (the meaning of words and phrases), and others are all subcategories of micro-linguistics.
In conclusion, macro-linguistics studies language and the influences on language in general, while micro-linguistics studies language and all of its properties, elements, and concepts in greater detail. Some argue that macro-linguistics focuses more on society and the way it influences language, while micro-linguistics focuses more on language itself and its elements.