Resale Tax Number + HST Exemption Certificate

I just started a store and I have been given a form to fill by a supplier.

I am based out of Calgary, AB Canada and the supplier is in Oakville, ON.

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I have been asked for a Resale Tax Number and HST exemption certificate.

According to https://www.retailcouncil.org/resources/quick-facts/sales-tax-rates-by-province/

There is no tax (PST or HST) in Alberta.

How do I handle this ? Do I need to call the provincial tax authority and look for HST exemption cert ?

What is a Resale Tax Number ?

Does this mean, if I make a sale in another province all the taxes from that region apply to my store sale ?

What about sales made in the US?