What is lubricating grease?

Lubricating grease is a mixture of three main components:  lubricating fluid, performance enhancing additives, and thickener.  The lubricating fluid can be petroleum-derived lubricating oil, any of various synthetic lubricating fluids, or vegetable-based oil.  The lubricating fluid is usually the majority component in the grease formulation.  The additives are typically present in relatively low concentrations, and are added to the grease to provide enhancement in one of multiple performance areas.  The thickener is what sets grease apart from liquid lubricants.  This component gives the grease the property of consistency, making the product semi-solid rather than liquid.  Many different chemical compounds can be used to thicken grease.  That subject is discussed separately.