Complex sentence: The Orbital part of inferior frontal gyrus is the part of the inferior frontal gyrus named opercularis (literally "the part that covers") because it covers part of the insula.
Split into simpler sentences: The orbital part of inferior frontal gyrus also known as the pars opercularis is the opercular part of the inferior frontal gyrus. Operculum means "the part that covers", because it covers part of the insula.