As a Shopware developer, your main work will be to develop extensions that enhance or modify the functionality of Shopware in a specific way. Shopware offers different ways of extensions, each with their own benefits and implications. To make sure you don't get lost within all the options, take a look at the Overview article which compares the approaches.
Alternatively, if you want to dive straight in, take a look at our introduction guides:
{% page-ref page="plugins/plugin-base-guide.md" %}
{% page-ref page="apps/app-base-guide.md" %}
{% page-ref page="themes/theme-base-guide.md" %}