This chapter discusses the informal logic and the concept of argument. According to its namers, informal logic "is best understood as the normative study of argument. It is the area of logic that seeks to develop standards, criteria and procedures for the interpretation, evaluation and construction of arguments and argumentation used in natural language." The research program of informal logic does not preclude the use of formal methods or appeal to formal logics. Its distinctiveness consists in its consideration of a set of questions that are not addressed in the specialist journals of formal logic. This chapter proposes a definition of an argument as a set of one or more interlinked premiss-illative-conclusion sequences. Such sequences can be interlinked either through chaining together, when the conclusion of one sequence is a premise of another, or through embedding, when one sequence is a premise of another. This chapter also elaborates concepts related to technical and everyday senses of "argument." Role of argument as discourse supporting a point of view by offering one or more reasons is explained. The concept of argument as invitations to inference is discussed.