The word 'set' has more definitions in the English language than any other word. Therefore, without a clear explanation of the types of 'sets' being asked about, it is impossible to be concise in an answer to this question. Given the various types of 'sets' we can provide a few answers as to how these specific types are used in our daily life:
In math there are sets of numbers, equations, and other factors that can be used in daily life for calculations whether it is to calculate the cost of something, income earnings, or other calculations based on circumstances in one's life.
Chinese medicine uses 'sets' to complete things they believe to be out of balance. One of the most important things to be balanced in Chinese culture is the body. If one part of the body is off balance, it will cause an illness; therefore, there is a 'set' of two things that provides this equality. It can be considered Yin and Yang in Asian cultures.
In science there are 'sets' of data. Data sets are a series of numbers obtained through an experiment. These sets do not have to be equal or balanced. They are just a series of numbers recorded based on the experiment and then later used to interpret the results of the experiment. They may also be calculated using mathematical sets to obtain relevant statistics such as the median.
There are school sets like flashcards, study tools, etc. That provide one with helpful tools to learn. These 'sets' are used in daily life to fulfill one's need for knowledge.