BADI: BADI (Business Add-in's)
BAPI : BAPI (Business Application Programming Interface)
ALV : ABAP List Viewer
ALE : Application Link Enabling
BAPI : It is used to transfer data between SAP systems and Non-SAP Systems and vice-versa.
Ex: If are using .net application where u want to connect the SAP system and retrieve the data and then change and updated in SAP system for that purpose we use this.
ALV : ALV reduce development time because Summing and column alignment ,coloring etc. will taken care by ALV. It have predefined Function Modules and SAP standard tablesFunction Modules used in ALV are:
REUSE_ALV_LIST_DISPLAY REUSE_ALV_GRID_DISPLAY REUSE_COMMENTARY_WRITE
REUSE_ALV_EVENT_GET...SAP STANDARD TABLES SLIS_T_FIELDCAT_ALV SLIS_T_LISTHEADER
It provide intelligent mechanisms where by client can achieve integration as well as distribution of applications and data.