What is Sufism or Tasawwuf
Professor Sayyed Hossein Nasr of George Washington University and an authority on Sufism, says Sufism or Tasawwuf is the name for the inner or esoteric dimension of Islam. Professor Allan Godlas of the University of Georgia says that Tasawwuf is the inner, mystical, or spiritual dimension of Islam.
An Islamic website says that Tasawwuf is the rooh (soul) and state of perfection of the Deen (religion). Its function is to purify the heart from anger, malice, hate, jealousy, greed, etc. and to fill it with truth, justice, compassion, forgiveness, Zikr (remembrance of God) and other virtues.
The way I understand it, Tasawwuf is necessary to build a foundation of our Deen(faith). It requires that we control our ego (Nafs) and get rid of the toxic trash/baggage* from our heart and replace it with compassion, humility, truth, forgiveness, gratitude, justice and other virtues and that will illuminate the heart and bring love of God. The fear of God leads to the love of God. One does not have to join a Sufi order to do Tasawwuf. .
*The toxic baggage is anger, hate, resentment malice, greed, jealousy, lust, ostentation, deception, backbiting and slander(gheebat) and other negative emotions.
PS. In Sufi poetry especially of Hafiz and Omar Khayyam there is lot of mention of wine, intoxication and love. But the wine they mention does not cone from a bottle . It is a spiritual state one reaches with Ibadat, devotion and Tasawwuf. Love is love of God(ishq e Allah).