Import/Export using Toad from ORACLE

I didnt get the  two lines, can you please specify, thank you

1)
.sql is a sql script file which has sql commands in it.
.dmp is the dump file created from oracle export.  The definition of toad export is different from oracle export. Toad just extracts the sql and puts it in a dump file. Where Oracle export uses an oracle utility called 'exp' that exports all the contents of the database in a propreitory format. Ofcourse if you open it, all may see is the sql commands, but it is formatted in a way that oracle 'imp' utility can read it and the insert the data in another database.

2)
Export table data -> creates INSERT (sql) statements that can be run against an existing table to insert the data.
Export table script -> reengineers the table and create a sql command, which you can run against another database and create the table structure.
export table as flat file -> creates a ascii extract of the data (doesnot contain sql commands).

3)
import source file -> this function imports source code for procedures, functions, packages, triggers and/or views from files into the database.
IMPORT TABLE DATA -> will run the sql (INSERT) statements against the table you are intending to import the data into

4)
The most reliable way to transfer tables from one database to other is using oracle utilities exp/imp. oracle utilities will take care of any dependencies like constraints, indexes, grants etc.,. You can certainly do this with TOAD, but it is a pain in the ass. oracle executables do this in a snap.

'exp user1/pass@db1 file=userexport.dmp log=userexport.log'
'imp user2/pass@db2 file=userexport.dmp log=userimport.log fromuser=user1 touser=user2'

Since you have tnsnames configured on your machine, you will be able to run these commands on your pc.

Also look at this post for additional ways of copying data from one db to another.
http://www.experts-exchange.com/Databases/Oracle/Q_21996708.html

one more question. Thank you for the details appreciate it very much, I have a script like this one:

CREATE TABLE PRD
(
  PRODUCT_INFO  VARCHAR2(40 BYTE)            NOT NULL,
  NUM     INTEGER                      NOT NULL,
  PRD_ID   VARCHAR2(40 BYTE)            NOT NULL
)
TABLESPACE DWI
PC    40
PCEE    10
INIT   1
MAXTRANS   255
STORAGE    (
            INITIAL          64K
            MIN       1
            MAXS       214xxxxx
            PCTINCREASE      0
            FREELISTS        1
            FREELIST GROUPS  1
            BUFFER_POOL      DEFAULT
           )
LOGGING
NOCACHE
NOPARALLEL
NOMONITORING;

I get error no tablespace exist. So if I create a table space named DWI, then run the above script. Also the tablespace entry is with all the table create scripts, and it is always the same entry, so why is it included with every create table script. thank you