Originally Posted by Core Rule Book, pg 276
You are restrained by a creature, effect, or trap. You can’t move,
and you take a –2 penalty to your Armor Class, attack rolls, Reflex
saving throws, initiative checks, and Dexterity-based skill and
ability checks, except those made to grapple your opponent in
turn or to escape a grapple (see Grapple on page 246). In addition,
you can’t take actions that require two hands (or other limbs) to
perform. You can’t make attacks of opportunity.
You can’t use Stealth to hide from the creature grappling you,
even if a special ability allows you to hide when you normally
couldn’t. If you become invisible, through a spell or other ability,
you gain a +2 circumstance bonus to your check to escape being
grappled, but you receive no other benefit.