Table Types and Line Type

Question

What is the need of Table Types,
when there is Tables.
Even when iam using in the Abap Programs in se38..
iam not getting any difference..
Even i want to about the use of Line type
when there is the structure..
iam sap 4.7 they gave that Table type describe the structure and
functional attributes  of an internal table.

Answer 1

Way: 1:
Go to SE84 --> Select ABAP Dict --> Table Types -->
Enter the short names like ORDER wih leading and ending * on the Table Types Field. ---> F8
This will bring all related entries of Table Types(Line Types) having ORDER has a part of its Name.
Way:2:
If you know the Table Name, then go SE11 --> Putch in the Table Name --> Press Display
Now put the cursor on the Table Name field, press CNTLSHFTF3, on the WHERE USED LIST Pop up, Select only the TABLE TYPE Option and press EXECUTE.
This will bring the Table Types and Line Types.
SAP Table Types
I. Transparent tables (BKPF, VBAK, VBAP, KNA1, COEP)
• Allows secondary indexes (SE11->Display Table->Indexes)
• Can be buffered (SE11->Display Table->technical settings) Heavily updated tables should not be buffered.
II. Pool Tables (match codes, look up tables)
• Should be accessed via primary key or
• Should be buffered (SE11->Display Table->technical settings)
• No secondary indexes
• Select * is Ok because all columns retrieved anyway
III. Cluster Tables (BSEG,BSEC)• Should be accessed via primary key - very fast retrieval otherwise very slow
• No secondary indexes
• Select * is Ok because all columns retrieved anyway. Performing an operation on multiple rows is more efficient than single row operations. Therefore you still want to select into an internal table. If many rows are being selected into the internal table, you might still like to retrieve specific columns to cut down on the memory required.
• Statistical SQL functions (SUM, AVG, MIN, MAX, etc) not supported
• Can not be buffered
IV. Buffered Tables (includes both Transparent & Pool Tables)
While buffering database tables in program memory (SELECT into internal table) is generally a good idea for performance, it is not always necessary. Some tables are already buffered in memory. These are mostly configuration tables. If a table is already buffered, then a select statement against it is very fast. To determine if a table is buffered, choose the 'technical settings' soft button from the data dictionary display of a table (SE12). Pool tables should all be buffered.
Table Types : A table type describes the structure and functional attributes of an internal table in ABAP. In ABAP programs you can reference a table type TTYP defined in the ABAP Dictionary with the command
DATA : itab TYPE TTYP.
Reafer these links below for clear ideas.
http://help.sap.com/saphelp_nw04/helpdata/en/fb/f14736a1f0ad1fe10000009b38f839/frameset.htm
http://help.sap.com/saphelp_nw04/helpdata/en/90/8d7304b1af11d194f600a0c929b3c3/frameset.htm
Thanks
Allot points if this helps!