ITS A TABLE WHICH HAS NO PRIMARY KEY AND A TEMPORARY ONES.
WE CAN HAVE ANY NUMBER OF DUPLICATE RECORDS WE WANT.

internal table is just a structure that exists only during
run-time.
it could be used as  a snapshot of database table.

cheers.
Aditya.

INTERNAL TABLE IS A DATA STRUCTURE USED TO STORE MULTIPLE 
RECORDS OF DATA IT MAY OR MAY NOT BE RELATED TO A DATABASE 
TABLE WE HAVE STANDARD SORTED AND HASHED INTERNAL TABLES.

Internal table is   the temparary table created in RAM of
application server while runtime which is used to do the
operation on thye data while processing.

Internal tables provide a means of taking data from a fixed 
structure and storing it in working memory in ABAP. The 
data is stored line by line in memory, and each line has 
the same structure. In ABAP, internal tables fulfill the 
function of arrays. Since they are dynamic data objects, 
they save the programmer the task of dynamic memory 
management in his or her programs. You should use internal 
tables whenever you want to process a dataset with a fixed 
structure within a program. A particularly important use 
for internal tables is for storing and formatting data from 
a database table within a program. They are also a good way 
of including very complicated data structures in an ABAP 
program

INTERNAL TABLE ALLOCATING EXTRA SIZE OF MEMEORY IN 
APPLICATION SERVER.BUT INTERNAL TABLE MEMORY IS TEMPORORY.
WHEN THE INTERNAL TABLE IS CREATED IT ALLOCATES MEMORY 
DURING RUNTIME AND THAT MEMORY IS DESTROYED WHEN THE 
PROGRAM IS ENDED.

internal table is allocating extra size of memory in 
application server.but this memory is temporary.
internal table memory is allocated during at the runtime.
when the program is closed internal table memory is 
destroyed.

Internal table is the temporary Storage area that exists 
only at program runtime.

It is a complex Data Object Used to Store multiple records
at program run time temporarily. Memory Allocation to
Internal Tables is done dynamically at run time Only.
Initial Default Size is 8K.

Internal Table Types are

1)Standard Tables
2)Sorted Tables
3)Hashed Tables.

An internal table is the temporary storage area or table 
which created in RAM of Aplication server that exists only 
program runtime.

Internal table is the temporary storage area or table which 
created in RAM of Application server that exists only 
program runtime.

There are 3 types of internal table:-

1)Standard Tables
2)Sorted Tables 
3)Hashed Tables

internal table is an array of structure and is used for data storing and processing during execution of program.

Ex: data : begin of itab occurs 3,
           a type i,
           b type i,
           end of itab.