Little graphics

I remember seeing a description of what the little graphics next to each post meant but cannot find it now? Can someone help?
For example, some posts have an envelope in various styles etc..

At the bottom of every forum you can see the descriptions

For example

Thanks; What about the other one with a small circle over the flap?

You posted to it.

https://discussions.virtualdr.com/im.../2004/07/4.gif