Why are messaged ‘Greyed’ in the threads?

I’ve noticed that a fair few messages in the threads are ‘Greyed-out’ (the lettering of the title and the message itself is show in grey and not the normal black), why is this…???

Hi @Stu93, can you please expand by giving an example or a link?

I suspect this is designed to help you identify what posts are new vs those you have already viewed or similar.