A rifugio is a staffed mountain hut: some are run by CAI (the Italian Alpine Club), many by families who have kept them for generations. Almost all serve half board (dinner, bed and breakfast), which is how most hut-to-hut walkers travel: you carry clothes, water and snacks, and the huts handle the rest.
Beds range from small rooms to classic mountain dorms; a sleeping-bag liner is required nearly everywhere and blankets are provided. The season runs roughly mid-June to late September, matching when the high trails are snow-free: outside those months most huts are shut and the plateau is winter terrain.
Expect roughly 60-80 EUR per person per night for half board, cash still preferred in some huts. The full breakdown, including drinks, showers and CAI discounts, is in the cost guide; how to behave in a dorm (the unwritten rules) is in rifugio etiquette.