...Is it an indication of how the marriage will progress or just the actual wedding? I was thinking it is the start of a new 'being' and so would signify how the couple would be together, rather like a composite chart or such. Mine has both a grand trine AND a grand square in it! what does that indicate?

Here it is for your perusal:

OOps I meant T-square not grand square. 

(can't find an edit button)

I don't know but I think looking at a wedding chart after the fact is a bit like doing an eye on the sky assessment about a day in the past.  You already know what the energy of the day was and how it all went and are likely beginning to get a handle on what the marriage will be like.  If not, synastry and composite charts are more likely to be helpful than rehashing the wedding day.

 I could be wrong and I'm certain people will step up and disagree if I am. 

Well, that's what I've been trying to figure out--whether the chart was more of a "what will this day/event be like?" or "what is this union going to be like?"

Thanks for trying to clear that up!