As reference you can use the following book:
Chapman, N. and Chapman, J. (2009), Digital Multimedia, 3rd edition, John Wiley & Sons, ISBN10: 0470858907 ISBN13: 978-0470858905
Assignment is:
By answering these questions I would like you to develop an argument for or against the use of browser application extensions.
Do you think there a real difference between a plug-in and a helper application?
What are the reasons for their development?
Is it a good thing to allow companies other than the manufacturer to extend your browser software?
Will HTML5 replace them altogether?