What does the speech bubbles mean?

[qball28]

There are red ones, grey ones, red with + signs etc. ❓❓❓

[i-love-my-sheep]

Not sure which ones you mean? The only ones I get are those wretched extremely annoying speech bubbles on the main forum pages. Those wretched extremely annoying ones that you can't turn on. Those wretched annoying ones that you keep clicking on when trying to click on the next new message. AARRGGGHHH! I HATE those things!!!

[thecatspjs]

if you hover over the speech bubbles - the red ones denote " hot topic with new content" 

the grey ones "topic with new content" 

not sure bout the red ones with postive signs ??

[i-love-my-sheep]

Oh now I know which ones the OP was talking about. I think it's actually an arrow next to the icon not a plus sign, which means you have left a reply in that thread.