The article serves as an introduction to the fundamental principles of PostgreSQL query planning and provides a guide on using the EXPLAIN commands. It explains how databases store data in structures called heaps and how PostgreSQL processes queries through parsing, planning, and execution. The query planner evaluates multiple paths to determine the most efficient execution plan, represented as a tree. The article highlights the importance of table statistics, maintained through operations like VACUUM and ANALYZE, to optimize query execution. It details how to use the EXPLAIN command in both the PSQL command line interface and the pgAdmin 4 GUI, noting that each interface offers different advantages for viewing and analyzing query plans. The article concludes by setting the stage for subsequent articles that will delve deeper into understanding and optimizing query plans.