An obeisance is an act, usually physical, showing dutiful obedience. A supplicant might perform obeisance, touching his face to the ground, before humbly asking for help.
Obeisance is often used in historical or religious contexts and often refers to bowing or kneeling. Figuratively, it means an act of respect though sometimes with the negative connotation of slavishly doing as expected. Your boyfriend might bring you and your mother flowers in obeisance to the idea that the parents should be courted as much as the child. Consumers who want this software must show obeisance to the Internet — it can't be bought in a store or anywhere else.