Introspection means "to look inside," and describes the act of thinking about your own actions or inner thoughts. When you examine what you do, say, think or feel and how it affects your life and the lives of others, that's introspection.
It's easy to piece together the meaning of the noun introspection. Consider that intro means "within," while spec is from the Latin for "look." So you can tell that the word means the act of "looking within." Introspection isn't "thinking about yourself" in the sense of calculating your own interests; it's more like searching inside in order to understand yourself — what some people mock as "navel gazing." Nineteenth-century philosopher William Godwin once said, “The philosophy of the wisest man that ever existed is mainly derived from the act of introspection.”