Union operations refer to a method in set theory where two or more sets are combined to form a new set that contains all the unique elements from each of the original sets. For example, if we have two sets, A, B, C and B, C, D, the union of these sets would be A, B, C, D. This operation is denoted by the symbol ∪. In programming and data management, union operations are often used in databases to merge results from different queries. For instance, when using SQL, the UNION command allows users to combine the results of two or more SELECT statements, ensuring that duplicate records are removed in the final output.