How does the new hunger and energy work?

[MagicManICT]

health works as it always has--soft hit points, which you can lose and gain from moment to moment; hard hit points, which require recovery methods when lost (which are tied to the "Wounds/Healing" system now); and max hit points (some wounds will apply based on max HP, not just current SHP or HHP).
Stamina--drains rapidly as you do tasks; refills with rest; can be refilled quickly by drinking
energy--the basis for healing (SHP only heal at 8000+) and starvation (<3000 if I recall right)
Hunger--how benficial food is for you. at 0 hunger, you get a 3x bonus to FEPs, with the bonus going lower every 100 points you fill it
Satiations--these decrease the benefit of foods eaten in the related category by the percentage amount shown; can be reduced with time or via a variety of drinks
experience points--used to fuel hearth magic and the study of curiosities; can be earned via questing, special events (one time and recurring), or as a gift from a sovereign realm.

The RoB wiki is still fairly accurate and updated. http://ringofbrodgar.com/wiki/Haven_and_Hearth_Wiki