An indication of topics within which I've made a post before? Is that what the "star" is supposed to be in front of the topic? If so, I think it's a little confusing as to me it would be like email, where I'd want to "star" items to review or that I'd like to follow. Or if it means I'm following them, then I'd like to know the difference, a notation for topics within which I've actually posted.

Yes that's what the star icon is.

which one? :-) is it topics that I am following or topics to which I've posted?

Topics you have posted in.