The realisation that this world is one of deception and distraction...distraction from the goal of the hereafter. A reminder that we often give preference to this (temporary) world over the ever-living joy of the Paradise.
Ākhirah - troid.org | Islamic Articles and Audio
Know this so that you will be able to answer the three questions which you will be asked in your grave. Who is your Lord? What is your Religion? Who is your Prophet?