The article discusses different types of market liquidity and how they are influenced by market structures. It explains the concept of dark liquidity and its role in trading securities. The researchers explore the need for market liquidity, issues like market impact and information leakage, and the basics of market microstructure. They focus on orders as instructions to buy and sell securities and how markets match buyers and sellers. The study also looks at liquidity supply and demand, considering factors like immediacy, depth, breadth, and resiliency. These topics will help in understanding pricing and execution in securities trading.