What is the difference between clearing cache, restarting the application, and restarting IIS?

In nopCommerce 4, What is the difference between clearing cache, restarting the application, and restarting IIS?  Sometimes I need to go all the way to restarting IIS when changes are made to the site. Sometimes simply restarting the application or clearing cache is sufficient.  Sometimes I don't need to do any of that.  I'm just trying to get an understanding of what they do and when I need to use them so I don't waste time.

Thanks!