Bold subject titles on posts

[happymom99]

Why are some subject titles bold and some are not?

Also, why do some subject has a little yellow chick next to them and some do not?

Thank you,
CJ

 

[Sorin]

You know, I kinda wondered that myself

 

[TM Chickens]

The threads that contain posts you haven't read will be bold until you read them.

 

[sourland]

And they will exhibit little yellow chicks.