It doesn't explain and it just pops up an "Are You Sure?"

 

That's invoice tracking, it'll send you an email when the invoice is paid.

But all gift cards are inherently paid - no paid invoice no gift card?

 

Your screenshot is showing the invoice row, this would be the invoice for purchasing a gift card.

7 minutes ago, Ocean West said:

Yes…. Notice how you’re viewing the INVOICE? Clicking the track button will track that invoice.  It does not matter what the product is…. You’re not tracking “Gift Card”.  You are tracking invoice 1554.  The invoice is paid now, but if it gets refunded for example…. 

In most cases though, there is not a lot of value in tracking a paid invoice.  Most people use it for unpaid invoices.  

What Randy says is correct there. You are tracking an invoice not the gift card. There are instances you may actually track an invoice which is already paid. For example, you may want to know if its refunded