In arabic literal meaning of khalifa is... A person who takes some one place when he left or died ...in english it is caliph
In islamic history khalifas were the four successors of prophet Mohammad pbuh ...hazrat abu bakar, hazrat umer, hazrat usman and hazrat ali respectively
They were religious and spritual leaders and as well as civil governors of islamic state...after these 4 holy person who ever governed the islamic state in which holy lands makka and madina present saudia arabs came self proclaimed them khalifa but they were monarchs ... Term khalifa is strictly use for religious leadership ... Successor of prophet...
Last self proclaimed khilafat was the ottoman empire ... Called khilafat e usmania of turki ..
Now i m not watching show so dont know where it used in show... If u can tell me the dialogue ...i can tell more specificly