The process of choosing the right indexes to use, and the right order to fetch data in, is called query planning. Query planning involves analyzing the input SQL code, breaking it down into a sequence of tokens, checking for semantic errors, optimizing the query plan, and generating an executable plan that specifies the steps the database engine should take to execute the query. The optimization phase is crucial as it determines the most efficient way to execute the query, considering factors such as available indexes, data distribution, and overall structure of the database. A good query planner can significantly impact the performance and efficiency of databases, making it an essential component of database management systems.