Plug-in's and Firmware

This is my first time logging and I just spent a great deal of time reading other Q & A's most awesome was of resolving problems.

I just had Dell this morning replace my mother board and also has to replace and re-install my hardware.  I am having problems  & confused keeping an icon for the internet as if I have not installed anything. Although I can get onto the internet I keep getting that I am working off line.  I am just confused because I was used to seeing my icons in the control panel and I don't no why I keep getting the "work offline status." At times thinking that I need to reinstall the correct icons I do get a message that states need to "add plug-ins"

 

What are plug -in  and I also need reinstall my linksys WRT54G router. I found the website to reinstall but do not know what is the firmware, do I need it, what is it?