sap memory is the total sap memory where as abap memory is 
confined to one session or we can say se38.
set parameter and get parameters are used to store the 
vaklue of  varable and transsport to  another session 
trheses are used as sap memory units
and import and export  are used  as abap memory units to 
transport

Ther are two types of memeorys available to us they are 

SAP memory
ABAP memory

Sap memory
This memory is the total sap memory i.e we can scroll 
through various sessions.

Whereas ABAP memory is confined only to one particular 
session i.e one tcode.

the memory allocated for all  prasentaion layers is called 
sap memory or shared memory
the memory allocated for each and every prasentaion layer 
is called abap memory or work process memory.

SAP memory is a memory area to which all main sessions 
within a SAPgui have access.You can use SAP memory either 
to pass data from one program to another within a session, 
or to pass data from one session to another.

ABAP memory is a memory area that all ABAP programs within 
the same internal session can access using the EXPORT and 
IMPORT statements.