The article considers and systematises theoretical approaches to determining clusters' nature and role in developing the regional economy. Based on the terminological analysis results, the cluster's main characteristics that underlie the definition of its essence are identified. These include the association (group) of interconnected enterprises; concentration by geographical or industry characteristics; competition; ensuring high competitiveness of products; synergy effect; cooperation; introduction of new technologies. To clarify the cluster's essence, the paper systematises scientists' views on its role in the region's economy. The author considered the effect of clusters at 3 levels: the enterprise (increasing competitiveness, sharing experience, increasing the level of specialisation, increasing turnover and product quality, etc.); state authorities (increasing budget revenues, reducing unemployment benefits, etc.); the economy of the region (reducing unemployment, improving the standard of living of the population, increasing the industrial, innovative, investment, and scientific potential of the region). The results obtained formed the basis for clarifying the essence of the concept of "cluster".