This document provides definitions for common terms used in the online advertising industry. It begins with an introduction stating that the online ad space uses complex terminology ("ad tech alphabet soup"). It then lists and defines key terms for both the buy-side and sell-side of the industry, such as RTB, DMP, PMP, DSP, SSP, and ad verification techniques. The document concludes by offering best practices for staying informed on industry terminology, such as challenging yourself to learn new terms, keeping a glossary, being curious, and reading trade publications regularly.