DBT Column Lineage is a tool designed to visualize column-level data lineage in dbt projects using dbt artifacts and SQL parsing. It offers an interactive explorer, DOT file generation, and text output for visualizing model and column dependencies. Users need to compile their dbt project and generate a catalog before using the tool to explore or analyze lineage.

SQL query optimization involves the DBMS determining the most efficient plan to execute a query, with the query optimizer responsible for evaluating different execution plans based on cost. The Plan Explorer tool, implemented for PostgreSQL, visualizes these plans and provides insights into the optimizer's decisions by generating various diagrams. The tool can operate in both standalone and server modes, enabling deeper analysis of query execution and costs.