Special Senses
Source Player Core pg. 424
While a human might have a difficult time making creatures out in dim light, an android can see those creatures just fine. And though androids have no problem seeing on a dimly lit street, their vision can't penetrate complete darkness, whereas a pahtra's can. Special senses allow a creature to ignore or reduce the effects of the undetected, hidden, or concealed conditions when it comes to situations that foil average vision.
Darkvision and Greater Darkvision
Source Player Core pg. 424
A creature with darkvision or greater darkvision can see perfectly well in areas of darkness and dim light, though such vision is in black and white only. Some forms of magical darkness, such as a 4th-rank darkness spell, block normal darkvision. A creature with greater darkvision, however, can see through even these forms of magical darkness.
Low-light Vision
Source Player Core pg. 425
A creature with low-light vision can see in dim light as though it were bright light, so it ignores the concealed condition due to dim light.
Scent
Source Player Core pg. 425
Scent involves sensing creatures or objects by smell, and is usually a vague sense. The range is listed in the ability, and it functions only if the creature or object being detected emits an aroma. If a creature emits a heavy aroma or is upwind, the GM can double or even triple the range of scent abilities used to detect that creature, and the GM can reduce the range if a creature is downwind.
Tremorsense
Source Player Core pg. 425
Tremorsense allows a creature to feel the vibrations through a solid surface caused by movement. It's usually an imprecise sense with a limited range (listed in the ability). Tremorsense functions only if the detecting creature is on the same surface as the subject, and only if the subject is moving along (or burrowing through) the surface.