Question

What is gyri and Sulci?where is it present?

Answer 1

Sulci (sing. sulcus) are the grooves, and 
gyri (sing. gyrus) are the folds or ridges that make up the folded surface of the cerebral cortex.
(present in : cerebral cortex.).

Answer 2

NCERT based Answer for Class 11 Biology Students

Gyri and sulci: During embryonic development, when brain size increases rapidly, the gray matter of cortex enlarges much faster than the deeper white matter. As a result, the cortical region forms folds. The upwards folds are called gyri (singular: gyrus) whereas downwards grooves are called sulci (singular: sulcus)