Adelic structures are mathematical constructs that arise in number theory, particularly in the study of algebraic numbers and algebraic varieties. They combine local and global properties of numbers by considering both the rational numbers and their completions at various places, such as the p-adic numbers and the real numbers. This approach allows mathematicians to analyze problems in a unified way. In essence, an adelic structure is formed by taking a product of local fields, which represent different places of a number field, and incorporating a global component. This framework is useful in understanding the behavior of L-functions and automorphic forms, providing insights into deep connections between number theory and other areas of mathematics.