You're likely thinking of a cleavage furrow, not a furrow in general. A furrow isn't a structure in the cell but rather a process that happens during cell division.

Here's the role of a cleavage furrow in cell division:

* Cytokinesis: Cytokinesis is the division of the cytoplasm, which occurs alongside nuclear division (mitosis or meiosis). It's the final step in cell division, resulting in two daughter cells.

* Formation: The cleavage furrow forms as a shallow groove on the cell surface during late anaphase or early telophase of mitosis or meiosis. It's caused by the constriction of a contractile ring made up of microfilaments (mainly actin) and myosin.

* Contraction: The contractile ring tightens like a drawstring, pulling the cell membrane inward. The furrow progressively deepens and eventually pinches off, completely separating the two daughter cells.

In essence, the cleavage furrow is the physical manifestation of cytokinesis, the process that divides the cytoplasm and creates two distinct cells from one.