WooCommerce is a plugin built by the developers of WordPress, for WordPress and turns the website publishing platform into a fully fledged online store.
WooCommerce is a free application which in its native form out of the box is fairly basic in it’s functionality.
Every online store has it’s own unique requirements, so the basic nature of the vanilla installation of WooCommerce allows you to add plugins that add additional features.
There are literally thousands of plugins available that add these new features, some are free, others are available either by annual subscription or a one off payment.
For approved plugins, check out the WooCommerce Extensions store to find out how easy it is to create an online store unique to your needs.