Difference between PSA and Commercial

1.  The difference between PSA and commercial is PSA is tried to warn of give information.
                                                Commercial tried to sell stuff that they are trying to sell.
                                               PSA tried to make people do something
2.  3 things that keep a PSA or Commercial:
      1.Theme
      2.Unique
      3. good information .
3.  2 things that make PSA and Commercial interesting on radio:
       1. Good sound effects
       2. Good description