Little pictures/icons next to names?

[Mathius]

When we post in a thread, there is a little silver or red/yellow/orange icon/picture thing next to everyone's names. What the heck is that little picture supposed to be?

They seem to indicate when someone is on or offline?

I mean these little things: https://www.pro-touring.com/forum/images/statusicon/user_online.gif

Mathius

[Damn True]

A hub, disk and caliper.

It's red (hot) if the person is online, silver (cold) if not.