The colored bar under the topic title is the Activity Meter. The bar length advances and the color moves to the warm side of the color wheel if the topic is a "hot" one. The threads with a longer red bar are the ones that have gotten an exorbitant amount of postings in a 24 hour period.
EvC doesn't offer a PM system at this time. It may be something on Admin's to do list, but I'm not sure.
Move your mouse over the "AM:" portion next to the bar. I tried to get the hover text to appear when the mouse is moved over any part of the bar, but some browsers don't respond to it.
If "PM" mean "private message", then the closest thing we have is the "mail" button that (sometimes) appears at the bottom (towards the left) of a post. This button appears only when a poster has chosen in his/her profile that he/she is willing to receive emails.
Clicking on the "mail" button will give you the email address of that user.