Primary attributes describe the character's abilities to fight, dodge,
learn spells, etc. They grow permanently from gaining levels, and may
increase temporarily from using appropriate artefacts or abilities. They
may decrease for various reasons, as well.

Your hero's primary attributes are Strength, Dexterity, Intelligence:

If any one of these drops to zero for some reason, you die. Note that
upon gaining Levels 3, 6, 9, etc., you get to choose an attribute to
raise. Random increases can also occur; which levels give an increase
is determined by species, as is the attribute to be increased. Crawl
has only three primary attributes:

They grow permanently from gaining levels, and may increase or decrease
temporarily from mutations or using appropriate artefacts or abilities.
If any one of these drops to zero for some reason, you die. This can be
a nasty and deadly surprise. As a rule of thumb, you are safe from this
type of death if all of your attributes are at least 7.
Upon gaining Levels 3, 6, 9, etc., you get to choose an attribute to
raise. Random increases can also occur; which levels give an increase
is determined by species, as is the attribute to be increased.

The next numbers shown are the Experience Pool and the (dungeon) Level:

expend some of your magical energy and become hungrier (although more
intelligent spellcasters hunger less quickly from using magic).

expend some of your magical energy and become hungrier (although high
intelligence and Spellcasting help against hunger from spells). Pressing
'II' (or 'I!') displays the hunger costs of your spells in terms of food,
on a rough scale of none, grape, apple, choko, ration.