Glomerular filtration is the process which kidneys uses to filter excess fluid and waste products out of the blood into the urine collecting tubules of the kidney, so that they may be eliminated from the body
The rate at which kidneys filter blood is called the glomerular filtration rate
The main driving force for the filtering process, or outward pressure is the blood pressure as it enters the glomerulus, this is counteracted to some extent by inward pressure due to the hydrostatic pressure of the fluid within the urinary space, and the pressure generated by the proteins left in the capillaries that tend to pull water back into the circulatory system (colloidal osmotic pressure)
The net filtration pressure is the outward pressure minus the inward pressure