Here, Odysseus describes the cyclops named Polyphemus, who is a son of Poseidon, the god of the sea. Of this monstrous creature, he says, to paraphrase:

This ponderously big monster man sleeps in his cave all by himself, taking his flocks of sheep to graze in a field far away from any of his fellow cyclopes, and this alienation means that the brute keeps his own, savage ways. He is so savage and different that he hardly seems like a regular man at all but, rather, like a solitary and boorish mountain.

He uses a metaphor, a comparison of two unalike things where one thing is said to be another, to compare the cyclops to a mountain, emphasizing his size and craggy appearance. Odysseus seems to want to establish the cyclops, right away, as different from him, his crew, and his audience. He seems to desire to prejudice his audience against Polyphemus in order to present him in as savage and unsympathetic a way as possible.

You tagged this with interpreting. I imagine you are looking for some help interpreting this quote from your literature book about The Cyclops section of The Odyssey.

First, you have some characterization of the cyclops named Polyphemus, but also cyclopes in general. They stick to themselve, and are very uncivilized. They have no remnants of culture that indicates they want to be together socially. We know this from the words, "alone", "remote", and "solitude". We learn that they raise sheep or goats as he toook his flocks to graze.

We also get the image and metaphor of the cyclops being a "shaggy mountain." This must mean he was rather large, mammoth to be specific. The word shaggy might describe a lazy, withdrawn, or haunched-looking fellow. It also further characterizes him.