A paralyzed character is frozen in place and unable to move or act. A paralyzed character has effective Dexterity and Strength scores of 0 and is helpless, but can take purely mental actions. A winged creature flying in the air at the time that it becomes paralyzed cannot flap its wings and falls. A paralyzed swimmer can't swim and may drown. A creature can move through a space occupied by a paralyzed creature—ally or not. Each square occupied by a paralyzed creature, however, counts as 2 squares to move through.

Marius, Scholai Armsmaster Says: You can coup de grace a paralyzed creature, dealing an automatic critical hit.  If you paralyze enemies frequently with spells like Hold Person, consider arming yourself with high crit weapons like axes, picks, punching daggers, and scythes.