Hi Francisco,
the languague that is used is Server-Side Javascript. It is javascript language + some special objects like request, response, db, trace, etc.
For documentation you can check SAP HANA Developer Guide at http://help.sap.com/hana_platform
You can also watch the online course "Introduction to Software Development on SAP HANA" from https://open.sap.com/
hope this will help you 
Stoyan