Extending PIMcore

Just wondering what is the process if there is some functionality missing in Pimcore…
Is it possible to write additional php code or most of the requirements should be done by configuration.
We are looking to implement PIM/MDM and DAM for our eCommerce store.
thanks

You can extend front and backend via Extensiond (Bundles) as described here:
https://pimcore.com/docs/5.x/Development_Documentation/Extending_Pimcore/index.html