What does Notify Me of Updates do?

I'm currently out of stock on a couple of items. If someone clicks the Notify Me of Updates, when I get stock and change the stock on hand to a positive number, will that be an update that they will be notified about? What will the Email say?

No. It simply puts the customer on a list of opt-ins for updates which you can send using the newsletter manager in Admin->Tools->Newsletters.

To do it, you'd compose a new "Product Notification" newsletter, and when selecting the desired recipients, you'll select which products the notification applies to. Then those customers will receive that newsletter when you send it.

If you want to tell them about new stock ... you'll have to do that manually.

At least, that's how it works presently.

If you want to do something like that, try the Request Restock module.

Thanks, Dr. Byte. It helps to know I'll need to notify customers manually. Once someone has requested updates on a product, will that appear as an option under "send email" like the various options that are already there? (all customers, newsletter subscribers, customers who haven't completed a purchase, individual customer names, etc.)

Yellow, I can barely manage the basic program. I did try to install the inventory-by-attribute mod and couldn't even figure out how to install it, so I'd better stick with the basics for now (although I appreciate the information).

I went into Admin/Tools/Newsletter and Product Notification Manager and created a notice that the product was back in stock (which it isn't yet, but I like having stuff ready) and saved it, but I didn't want to click "send" yet and didn't know how it would work. But amazingly (because search functions don't like me), I found a FAQ about it:

https://www.zen-cart.com/tutorials/index.php?article=220

According to this, since I set the type of newsletter as a Product Notification, when I click "send" I'll be able to select the products the notice (in this case, a Back In Stock announcement) applies to. Cool!