Sleeping in a bed fast forwards you in game time to the next morning so that you get the rested buff. The presence of the bed increases your comfort level by one so the rested buff lasts a minute longer. Finally, you must have a fire in the immediate vicinity and make the bed your spawn point to sleep in it.

If I have a small shelter with a fire and a bed, I can claim the bed, sleep in it, and wake up the next morning with the rested buff for eleven minutes.

If I have a small shelter with a fire, I can plant my butt next to the fire, twiddle my thumbs until the next morning and start out with the rested buff for ten minutes. One minute less than if I slept.

If I build a bed but don't claim it, I increase my comfort level by one. Then if I plant my butt next to the fire and twiddle my thumbs until the next morning, I start out with the same eleven minute rested buff that I would have had if I had slept. No difference except that If I die, I should respawn elsewhere. Hopefully, in my elaborately constructed and furnished main base where all my spare food, gear, and collected resources are stored.

Does anyone know the Norse word for insomniac? Leif the Baggy-Eyed doesn't sound quite right.