As far as I know,

It’s basically a way to sell stuff online, like Etsy. You set up a website with them, then you have a “store” where customers can order things from Shopify.

I assume you’ll have to give them your bank account information to get payments, and I’m sure Shopify will charge you monthly to have your work on their platform.

Also, keep in mind that they will probably take a fee out of every sale, like a traditional art gallery would take a percentage of each sale for the privilege of having your work displayed in their gallery.