Pluralism is the idea that reality consists of different kinds of things. The term is used in different fields of study. Social pluralism deals with the many different types of social structure. Cultural pluralism deals with the many different types of culture, etc.
Pluralism has many meanings as it is applied to different areas of study: economic, religious, political, educational, etc. But generally, pluralism is the position that there is a broad range of views and/or positions that are valid when considering to explain and/or understand something. In philosophy, it is the teaching that there is more than one basic substance to reality.