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.
Zendesk is a customer support tool. It's got 2 main features: ticketing and knowledge base. Ticketing: Zendesk gathers customer queries in one place where you can manage and respond to customer questions efficiently. Knowledge base allows you to create an FAQ section to guide your customers.
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.
The Geolocation app lets you recommend the best language & currency for your visitors based on their browser preferences and location. These recommendations show up on your store as a bar or popup. Your visitors can also change language and currency anytime with selectors, which work with any theme.