This paper introduces cluster algebras, a new class of commutative algebras, as an algebraic framework for dual canonical bases and total positivity in semisimple groups. The paper outlines the foundational concepts and properties of cluster algebras, including their definition, exchange relations, and the Laurent phenomenon. A cluster algebra of rank n is a commutative ring with unit and no zero divisors, equipped with a distinguished family of generators called cluster variables. These variables are organized into clusters, which have an exchange property: any cluster variable can be replaced by another variable related by a binomial exchange relation. The prototypical example is the coordinate ring of SL₂, where the exchange relation is ad = 1 + bc. Another example is the coordinate ring of SL₃/N, where the exchange relation is x₂x₁₃ = x₁x₂₃ + x₃x₁₂. The paper discusses the Laurent phenomenon, which states that any cluster variable can be expressed as a Laurent polynomial in the variables of any given cluster. This property is crucial for the study of dual canonical bases and total positivity. The paper also explores the connections between cluster algebras and Kac-Moody algebras, and shows that cluster algebras of rank 2 have deep connections with these structures. The paper introduces the concept of exchange patterns, which are families of monomials satisfying certain axioms. These patterns are used to define cluster algebras, and the paper discusses the properties of these patterns, including their relation to the Laurent phenomenon and the exchange relations. The paper also discusses the structure of cluster algebras, including their classification and the role of the exchange graph. It concludes with the conjecture that the coordinate rings of many interesting varieties related to semisimple groups have a natural structure of a cluster algebra. This structure is expected to serve as an algebraic framework for the study of dual canonical bases and their q-deformations.This paper introduces cluster algebras, a new class of commutative algebras, as an algebraic framework for dual canonical bases and total positivity in semisimple groups. The paper outlines the foundational concepts and properties of cluster algebras, including their definition, exchange relations, and the Laurent phenomenon. A cluster algebra of rank n is a commutative ring with unit and no zero divisors, equipped with a distinguished family of generators called cluster variables. These variables are organized into clusters, which have an exchange property: any cluster variable can be replaced by another variable related by a binomial exchange relation. The prototypical example is the coordinate ring of SL₂, where the exchange relation is ad = 1 + bc. Another example is the coordinate ring of SL₃/N, where the exchange relation is x₂x₁₃ = x₁x₂₃ + x₃x₁₂. The paper discusses the Laurent phenomenon, which states that any cluster variable can be expressed as a Laurent polynomial in the variables of any given cluster. This property is crucial for the study of dual canonical bases and total positivity. The paper also explores the connections between cluster algebras and Kac-Moody algebras, and shows that cluster algebras of rank 2 have deep connections with these structures. The paper introduces the concept of exchange patterns, which are families of monomials satisfying certain axioms. These patterns are used to define cluster algebras, and the paper discusses the properties of these patterns, including their relation to the Laurent phenomenon and the exchange relations. The paper also discusses the structure of cluster algebras, including their classification and the role of the exchange graph. It concludes with the conjecture that the coordinate rings of many interesting varieties related to semisimple groups have a natural structure of a cluster algebra. This structure is expected to serve as an algebraic framework for the study of dual canonical bases and their q-deformations.