Attempt to provide simplified explanation:
SAP
Now, that SAP has created an environment around SAP. In order to operate in SAP environment (i.e. for customisations etc.), language-abstraction was required. Here comes ABAP.
ABAP
Therefore, any customisation on the basic version of SAP given to some customer of SAP would require ABAP usage, otherwise, just delivered SAP is good enough for usage (i.e. no ABAP required).
Now is another term HANA.
HANA
SAP and HANA together abstracts the underlying complexity of database-access queries and UI (developed in java), together, to make the user experience good for the management system (used majorly in analytics, and so that the main focus stays in analytics). This very specific tool/product, is said as "technology", as it has an environment of its own (terminologies etc.). ABAP facilitates further development of the SAP-ERP.
The underlying development is in C, C++ (and ABAP) for SAP.