when we talk regarding partner functions ,like in SD module 
are Bill to party , sold to party ,ship to party (these are 
partner functions .the output of one function is the input 
for another .

for getting the partner function details,follows the detail 
and table name.

vbpa==sd partner functions
knvp == customer partner functions
EKPA = Partner Roles in Purchasing
WYT3 = vendor partner function

Actually we are differentiating customer as partner 
profile , ie ship-to-party, sold-to-party, Forwarding 
agent. All this partner functions will be stored in VBPA 
table for a perticular sales order

data sturcture:
data structure is nothing but its create only  at runtime.
it doesnot allocate  the memory. and also it contains no 
data. because of its only structure.no memory is allocated 
for the sturcture.

data table:its nothing but sap predefined the table.
its allocated the memory at the runtime.while u defining 
the data table u can assign the table type ,length.
these all tables are stored into the database.