Delete  is DML command  used to delete rows from a table. A where clause can be used to remove some  rows.If no where clause is specified all rows will be removed.After delete operation you need to commit or Rollback the transaction to make the transaction permanent or to undo it.

On the other hand Truncate is a DDL Command remove all rows from the table.The operation cannot be rolled back.As such truncate is faster and does not use as much undo space as delete.

delete is DML cmd so we hav to save after delete i.e. no autosave

truncate is DDL cmd so autosave

and truncate is faster than delete

bcoz delete cmd deletes rows one by one 

Truncate is faster than delete because the Delete command deletes the records row by row

and command truncate delete all at once