What is the defanition of "Unread Posts?"

[#1]

Only ask, as clicked on unread posts, page opens titled "Recent Unread Topics".
Yet most appear to of been read/replied within the last hour or two!
As such would not fall into the category of "Unread".

[#2]

It's posts that you personally have not read

[#3]

Ahhhh Makes sense....
Thank you