I don't really know. this part is not even slightly confusing, and hasn't been much more clear after street magic.
Astral Com bat
Astral combat is resolved in the same way as physical combat. Astrally
perceiving and dual-natured characters use their Physical attributes
and skills to fight opponents with a physical body, and their Astral
Combat + Willpower to fight wholly astral entities. Astrally projecting
characters use their Mental attributes in place of Physical ones (see
the Astral Attributes Table, above) along with the Astral Combat skill.
There are no known ranged weapons that function in astral space, so
unarmed attacks, active weapon foci (p. 199), and mana spells are the
only options for astral combat.
Most astral combat damage is based on the character’s astral
strength (Charisma), as noted on the Astral Combat table. Damage
inflicted from astral combat attacks can be either Stun or Physical
(attacker’s choice). Astral objects like barriers can only be affected by
Physical damage.