This lecture explores the concept of vectorization in query processing within database systems, comparing tuple-at-a-time and column-at-a-time execution models. It delves into the vectorization model, which emits a vector of tuples per operator, optimizing performance by processing multiple tuples at a time. The instructor presents the advantages of vectorization for OLAP queries, highlighting the reduction in operator invocations and the utilization of vectorized instructions for batch processing.