Site navigation, icons, etc.

Where can I find out what the column of icons on the left side mean?  Also, why do some thread topics show up as red, while others are yellow? Nothing in the FAQs. Is there a section explaining how to navigate this site? Thanks.

Here is what I came up with. Yellow square-you have read it. Red square-new post since last visit. If there is a small white icon beside the topic title then you have posted in it. The black arrow and yellow icon beside the topic title I am not sure of.

Thank you. I would think there is a place here where that information can be read. Hopefully a moderator will join in.

On the left side any thread topic listing is an icon that says "View newest post", and on the right side is an icon that says "View latest post". WTF? Can anyone explain this?