This document provides a summary of lubrication and lubricants. It discusses the importance of lubrication for minimizing wear in machines. The key types of lubricants are liquids like oils and greases, as well as solids. Selection of the proper lubricant depends on factors like operating conditions, material compatibility, and environment. Oils and greases each have advantages and greases are suited for applications where accessibility is limited or lubrication intervals are long. The document outlines various lubrication principles including hydrodynamic, hydrostatic, and elasto-hydrodynamic film lubrication which generate pressure to separate machine surfaces.