Microeconomics is a branch of economic theory that is centred in modelling the interactions amongst market agents, specially between consumers, which are trying to maximise their utility, and firms, which try to maximise their profits. It analyses the underlying logic of the individual behaviour of economic agents such as the employer, the consumer, etc., and the notions that derive from them, such as, profit, utility, market structures, etc. In its purest form it answers the philosophical question regarding the resources allocation process.
The line that separates microeconomics from macroeconomics has become increasingly narrow throughout time. Nevertheless, it has always existed, and most probably will always exist, as some barriers are insurmountable. The goal of macroeconomics is to understand and predict the behaviour of economic variables in its aggregate terms. Therefore we make the distinction of microeconomics as relating to individual, micro, terms (consumers, firms, etc.), while macroeconomics relate to aggregate, macro, variables (consumption, unemployment, investment, etc.). A way to view both terms is from a disaggregated vs. aggregated perspective.
The methods and tools used in microeconomics are mainly the construction of models that simplify the reality so that the interdependence between variables can be analysed and represented. Many techniques may be used for the construction of these models; however, the great majority of them fall into the categories of optimisation analysis and equilibrium analysis. Furthermore, models of optimising behaviour represent nearly all of the models of individual behaviour in microeconomics.