Magento developers work to build, support and improve Magento websites. Many store owners hire them in order to improve their Magento business model. An experienced developer has the capacity to create, improve, and maintain an online store.
They focus on the looks and overall functionality of an ecommerce site.  Their role can at times be indispensable. They can work alone but in most cases, they are a part of a team within a company. Merchants usually hire a company to create or improve their web stores.