Step 1: Define the term functionally:
A Sufi can be understood as a seeker who prioritised inward devotion and love of God over outward ritual and legalism within Islam.
Step 2: Trace the historical arc:
Sufism's growth can be traced in three stages: early ascetic piety (8th-9th c.), the emergence of organised orders/silsilahs (from the 12th c.), and their spread into regions like India, where the Chishti order under Moinuddin Chishti became dominant.
Step 3: Highlight Indian adaptation:
In India, Sufi khanqahs became centres of interfaith exchange, blending with local Bhakti traditions, using vernacular language and music (qawwali) to reach ordinary people rather than only the elite.
Step 4: Conclude on legacy:
This made Sufism a major force for religious syncretism and social bonding in medieval Indian society.
Final Answer:
\[ \boxed{\text{Sufis were mystic seekers of divine love; Sufism grew from ascetic roots into organised orders like the Chishtis, which deeply influenced Indian religious culture}} \]