Q. What is Sufi ?

Response: Tasawwuf, a term meaning literally to clothe oneself in coarse wool garments may help to explain intention. Less a destination than a direct heightened experience of the physical in the moment to impel our spirits toward the Divine; Sufism is a garment of Secret Knowledge that is like Grace. IT is more bestowed than earned.

Q. What does Islam have to do with it ?

Response : In a purely rhetorical sense, as Christianity "existed" before Jesus in the prophetic scriptures of Judaism, Sufism (the kernel) existed before Muhammad (PBUH). However, it was in the folds of Islam that Sufism blossomed and flourished. When the dialogue began between Imam and Dervish / Seeker - Sufism began the Quest for definition. The rest is an academic conundrum.