I Have mentioned karaka's on a few occasions regarding Jyotish.
There are 3 types -
Naisargika or natural -shows everything that exists in creation. This is represented/owned by Brahma , since He is the author of all this creation. All 9 graha's are considered in this scheme.
Chara - are variable - there are 8 graha's ( Ketu is not included here) and are ruled by Vishnu. These chara karaka's indicate who influences the native in this life. Visnu rules over sustenance, maintenance and spiritual progress, these charakaraka point out these influences in one's chart.
Sthira - are fixed. There are 7 graha's in this category and are ruled by Siva. These fixed karka's show the destruction of the body , hence Rudra plays a key role. Rahu and Ketu are not part of the 7, as they do not have physical bodes (e.g. moon or Chandra is of material origin, size, weight, mass, etc). These sthira-karaka assists the Jyotisha in determining the death of the body.
So, this karaka is the significator, indicator or one who causes an event , situation or condition. We have natural, variable and fixed as mentioned above. The Charakaraka are of great import to the sadhu as it points out some key influences:
Atmakaraka - the SELF
Amatyakaraka - the Advisors ( guru's and the like)
Bhratrikaraka - Siblings
Matrikaraka - Mother or Mother figure ( nurturing)
Pitrikaraka - Father and/or Father figure ( a boss, leader, etc)
Putrakaraka - Children or Child like ( followers, sisya)
Jnatikaraka - Rivals
Darakarka - Spouse or the like ( married to or devoted to)
What is of interest is the Atmakarka for the sadhu - as this also assists one on determining the Ishtadevata from a Jyotish perspective. If one wishes to read this information please consider the following Ishtadevata specific posts:
When a Jyotish uses the Naisargika or natural karaka system, he/she looks at each graha and its indication/signification it plays in one's chart:
Sun: Ravi or Surya- Atma, physical constitution, eyes-seeing, health, east direction and dawn : Karaka of the 1st house ( Lagna), 10th (Career), 9th, and 5th houses.
Jupiter: Guru or Brihaspati - Family, wealth matters, expansion children, guru-teachers, religion, fortune, elder brothers: Karakak of the 2nd , 5th, 9th, and 11th houses. The NE direction.
Mars: Mangala - Courage, younger siblings, strength or stamina, blood, defense, enemies: Karaka of the 3rd, 6th, 4th, 5th houses. The S direction.
Moon: Chandra - Mother, compassion, feelings, mind & emotions, milk and ghee (soma too!), pearls, the evening: Karaka of the 4th, 1st and 11th houses, and the NW direction.
Venus: Sukla -wife and husband, martial relationships, vehicles, pleasures of the bed, fluids, perfumes, dance , music, song, e.g. feeding the senses: Karaka of the 7th house, 4th house, 12 house . The SE direction.
Mercury: Buddha - speech, learning, memory, credits, honors, friends, business, adeptness, mathematics: Karaka of the 2nd, 4th, 5th, 10th and 11th houses and owner of the North direction.
Saturn: Sani - longevity, troubles, grief, losses, ailments, limps, dishonor or fall from grace, hard labor, imprisonment, renunciation, one-pointedness. Karaka of the 8th, 6th, 5th and 12th and the West direction.
Rahu: accidents, occult knowledge, life in a foreign land, poisons, skin dis-eases, arguments, darkness. Karaka of the 7th, 9th and 6th houses. Owns the SW direction.
Ketu:- occult knowledge, moksha, detachment, fastidious, imprisonment. Karka of the 12th, 9th and 8th houses. Owns the NW direction.
I will add to this conversation to round out the discussion.