There are many different variants of Others, most of which can be countered by borrowed abilities using the SAS Brain Communication.
The Others fell from space a number of years ago. They seemed to be unstoppable for a number of years until something naturally triggered a part of the brain, granting a few people special abilities. These people banded together to become the Other Suppression Force (OSF) and their job is to utilise their powers to stop the Others.
Some Others are covered in armour, whereas different variations may have something that can leave them exposed to deal critical damage. Others with armour can be quickly taken down with Kyoka's Duplication or Gemma's Sclerokinesis.
Others with armour plates or hiding spots are extremely resistant to damage. However, the armour can be destroyed to expose a critical spot.