Almost an universal form of worship, circumambulation is the act of moving around or lapping a place or object of spiritual significance. This is most often done as part a pilgrimage. In Islam, the most important example of this, is when pilgrims circumambulate the Kaaba seven times as part of the Hajj.
In the case of Humayun's Tomb, circumambulation is carried over from that practiced at sufi holy sites and "was a common practice at Mughal imperial tombs."1
A circumambulatory path is an area designed to facilitate circumambulation.
1. Catherine Asher, The Architecture of Mughal India (Cambridge: Cambridge University Press, 1992), 56.
Parodi, Laura E. "The Posthumous Portrait of â€˜Hadrat Jannat Ashiyaniâ€™: Dynastic, Saintly, and Literary Imagery in the Tomb of Humayun." Islamic Art 6, (2009): 129-58.
Ruggles, D. Fairchild. "Humayun's Tomb and Garden: Typologies and Visual Order." In Gardens in the Time of the Great Muslim Empires, edited by Attioli Petruccioli, 173-86. Leiden: E. J. Brill, 1997.