Sufism (Tasawwuf) is a an emphasis on spirituality or mysticism through certain practices like wearing specific type of clothing, minimizing worldly possessions, and doing additional worship in a particular way. It may or may not be associated with a spiritual mentor or a movement (tariqah) like the Qadiri, Naqshabandi or Chisti. Some types of Sufism are completely in line with Islam, others are questionable, and yet others are outright deviance away from Islam. If the practice of Sufism strictly conforms with the teachings of the Qur’an and Sunnah of the Prophet Muhammad then it is fine, such as that practiced by early Sufi scholars like Harith Al-Muhasibi (d. 243/857), Junayd Al-Baghdadi (d. 298/910), Abdul Qadir Jaylani (d. 561/1166).
Be very careful of getting sucked into a Sufi cult where you are not allowed to ask questions or where there are not properly trained and recognized Muslims scholars associated with it.
Shaykh Mustafa Umar