Shopify app development is the process of building custom applications that extend a Shopify store's functionality, whether that's a custom internal tool, a merchant-facing feature, or a connection to another business system.

A custom app is built for a single store's specific requirement and installed directly to that store, rather than distributed publicly through the Shopify App Store. This is the current term for what used to be called a private app.

A custom app makes sense when a requirement needs functionality, data persistence, or an integration that theme customization or an existing app can't provide, such as a specific internal workflow or a connection to a system Shopify doesn't natively support.

A theme controls how your storefront looks and how shoppers experience it. An app adds functionality, workflows, or integrations that typically need to work independently of storefront styling.

Yes, in most cases, through Shopify's APIs and the external system's own API. Whether a specific integration is possible depends on what both platforms expose, and this is confirmed during planning rather than assumed.

Yes, custom apps are commonly used to automate order processing, data synchronization, and notifications, though the specific automation possible depends on your store's setup and the systems involved.

Yes. Shopify Plus businesses often need more advanced integrations or custom operational tools, though some Plus-specific requirements are better handled through other services like checkout customization or B2B development.

Primarily the Admin API, now built on GraphQL as Shopify's current standard, along with the Storefront API and webhooks depending on what the app needs to do.

Testing covers functional behavior and error handling before deployment. After launch, ongoing maintenance keeps the app compatible as Shopify updates its platform and APIs over time.