Hei vs He - What's the difference?

Kia ora ra e te iwi!This week I look at 'Hei' and 'He'.It's taken me a few years to begin grasping the nuances, so I thought I was speak on it today, hopefully solidifying my own understanding. Also hopefully, what I say is coherrent and makes sense haha.Anyways as always, here are my citations from Te Wiremu, though the english is my interpretation of the maori provided by Te Wiremu.Hei: [H.W. WIlliams, A Dictionary of the Maori Language, pg.44] Indictating future place and time.1. Hei te po taua hoe ai. - At night we shall ride (our waka).2. Hei konei na, he pa mo tatou. - Here at that place shall a pa be established for us.Indicating purpose and/or intention.1. Kei te rou kakahi hei o ki te taiapu. - Let us go musseling so we have some takeaway food for the raid.2. Ko wai tou tangata hei tangi i a koe, hei ngaki hoki i tou mate? - Who shall be the one that mourns for you, that goes all in for you when you die?indicating a future imperative1. Tikina he toki; hei te mea nui. - Fetch an axe; get a big one.2. Kaua hei tutu; whakatupu tangata. - Don't be a tutu; grow up and be someone we can be proud of.3. Kua katohia he putiputi hei hari atu ki te urupa. (This example came from He Pataka Kupu) - Cut some flowers so we can bring it to the urupa.He: [H.W. WIlliams, A Dictionary of the Maori Language, pg.43] An indefinite article, both singular and plural.1. He matau ano ra tahaku. - A fish hook is indeed in my possession.2. He tangata roroa enei tangata. - Some tall people these people are.3. Nga kai o tera maunga, he kiwi, he weka, he kiore, he kuku, he tui. - The foodsources of that mountain include kiwi, weka, kiore, kuku, and tui.4. Homai he wai moku. - Fetch some water for me.