What is the difference between drop,delete and truncate.. Can anyone tell why we require exists with example?can we rollback after commit?

What is the difference between drop,delete and truncate.. Can anyone tell
why we require exists with example?can we rollback after commit?

*Delete is a DML(Data Manipulation Language). Delete command is deletes
the record from the existing table.*The systax for Delete is
1)sql> Delete from .
This Deletes All the Record From The TAble
2) s*ql> Delete from Where*
This deletes a perticular set of record.
Note:Delete is not Autocommit Statment(Infact None os the DML are auto
commit)
Drop and Truncate both are DDL(Data Definition Language).
Drop {Delete or drops} the table with it's structure. It is as autocommit
statment.Drops Once fired can not be rolled back.
syntax:
sql>drop table
Trucate is the command used to delete all record from table. but the
structure of the table remain same.It is also a autocommit statment.
syntax;
sql>truncate table
Can we rollback the truncate?