1) Query optimization involves determining the most efficient execution plan for a query by considering factors like I/O cost, CPU cost, and communication cost. 2) There are different strategies for executing a query such as performing selections before joins to avoid unnecessary operations. Determining the optimal strategy involves minimizing a cost function. 3) Issues in distributed query optimization include where computation is performed (distributed vs centralized), when optimization occurs (static vs dynamic), and how to minimize expensive communication costs over wide area networks.