What is the difference between seeking Allah's help (isti'anah), relying on Allah (tawakkul), and supplicating (du'a)?

Supplication falls under seeking assistance (isti'anah), because seeking assistance is a request for help from Allah. Ibn Al-Qayyim equated reliance on Allah (tawakkul) with seeking assistance; seeking assistance combines trust in Allah and dependence on Him, which are the foundation of reliance and the essence of "You alone we worship and You alone we ask for help." Allah has linked reliance with worship in several places in the Quran, such as: (And my success is not but through Allah. Upon Him I have relied, and to Him I return), and (So worship Him and rely upon Him), and (Our Lord, upon You we have relied, and to You we have returned, and to You is the destination), and (Say, "He is my Lord; there is no deity except Him. Upon Him I have relied, and to Him is my return").