This document provides an overview of cerebrospinal fluid (CSF). It discusses the composition, formation, circulation, absorption, and functions of CSF. CSF is formed in the choroid plexus at a rate of around 500mL per day. It circulates through the ventricles of the brain and spinal cord before being absorbed into the bloodstream via arachnoid villi. CSF acts as a cushion or buffer for the brain, circulating nutrients and waste. The normal pressure of CSF is 130mm Hg when horizontal but it can vary from 65mm Hg up to 195mm Hg. Changes in CSF pressure can cause issues like hydrocephalus, brain edema, or papilledema.