The text discusses the `UNION` clause in Cypher, a query language used in Neo4j graph databases. The author highlights the issue of applying post-processing operations like sorting and pagination to the results of multiple queries combined using `UNION`. To resolve this, the author proposes rewriting the query using the `COLLECT` function and the `UNWIND` clause. By collecting values into a list with `COLLECT`, then unwinding it back into individual rows with `UNWIND`, and finally deconstructing the maps into columns again with `WITH`, the author demonstrates how to perform post-processing operations on the combined results of multiple queries. This approach allows for more flexibility and efficiency in processing the data, enabling sorting, pagination, filtering, and other aggregate functions to be applied to the results.