Kartik Night is a festival that celebrates the Ras Lila between Krishna and the gopis. It is symbolic of the supreme Love relationship between a bhakta and the Lord. On this night, we celebrate Krishna as the centre point of our lives and express our love and devotion to Him in the form of a large oil lamp made up dozens of small individual lamps representing the bhaktas.
Kartik month is a time when Lord Krishna makes Himself more available to His devotees than at any other time of the year. During this time, whatever you do in remembrance of Krishna will bear merits a hundred times more than usual, even for the smallest of offerings.
As He blesses all immensely during Kartik, it is considered most auspicious to stay awake all night to praising Him and dancing the Raas with Him. Many devotees also undertake special austerities such as fasting during the month-long event.