I have answered a very similar question in details and with pictures. But my obsession with Rahu, Ketu and Shani doesn’t let me pass any question related to them.
Here’s the deal: You can’t understand astrology without understanding the Mythology of it.
Demon Swarbhanu was behaded by Vishnu when he cheated Vishu and took Amrit (necter of immortality) . However, by that time he had become an immortal thus he couldn’t die.
The Head of Swarbhau became Rahu and the headless body became Ketu.
However, they are two archetypes representing to opposing sides of a man:
Rahu: a grossly materialistic side (ALL HEAD-NO HEART=RAHU) (Remember your empty suit of a boss who screams a lot and bullies the small guy and does nothing but plays politics, scheming and scamming all the time, That’s Rahu type for you )
Ketu: (No Head-All Spirit→The God’s Fool). Need nothing ascetic type. This is what Ketu represents. The ascetics, monks and those who give up on the world and pursue the spiritual side.
They belong to the same person but never do they meet. A deep philosophical, astrological and psychological concept.