Coop Commerce is reinventing the world of brand partnerships. With Coop, after a customer checks out, they see products from partner brands. The customer can view or purchase products from those brands which earns you coop credits. You can then use those credits for placements on partner sites.
Klaviyo is the best in class email marketing solution for eCommerce. It's powerful because it connects to your store, and you can create awesome customer segments based on past purchasing behaviors, customer preferences, and even future predictions of spending.
Shopify is a commerce platform that allows anyone to set up an online store and sell their products. It's the go-to eCommerce platform for young direct-to-consumer brands. It's ease of use and setup is what's most attractive to merchants, but also the incredibly vast Shopify app store.