One of the strangest things for me (as an American) to wrap my head around was the Belgian custom of inviting different people to different wedding events.
Where I come from, a wedding is considered a single event comprised of different activities, to which all guests are invited and expected to attend. The usual sequence goes something like this: wedding service (civil or religious) followed by wedding reception, either at the same venue or a different location. The reception usually involves drinks (champagne), then a formal dinner, and finally dancing.
Here in Belgium, it is customary to have a different guest list for each wedding activity. For instance, pretty much everyone is invited to attend the civil ceremony; there's no cost to the couple and because it takes place in a public venue (at city hall) anyone can show up and watch. On the other hand, if there's going to be another ceremony (in a church) only close friends and family might be invited and expected to attend. In general, people outside the couple's immediate circle are happy to skip the church ceremony.
Then there might be two or three different celebratory events after the ceremony (or ceremonies). First, a champagne reception for the people invited to the church ceremony. Then a formal dinner for just the immediate family and closest friends. And finally an evening party with music and dancing for the wider circle of friends, acquaintances and other relatives. (At the evening party, there will often be a casual buffet served late in the evening with sandwiches or snacks.)
Breaking the wedding up into different events (sometimes taking place over two or more days) has two advantages: First of all, you can tailor the guest list to the event, limiting the more intimate events to your inner circle of family and friends and including everyone else in a big dance party. Secondly, it saves money since you're not expected or obliged to provide a formal, sit-down dinner to all of your guests--which is often the biggest wedding expense. It's a very practical system.
In the end, because our second ceremony took place in the same location (an old, renovated farmhouse) where we had the reception and party, it didn't make sense to break up the guest list anyway. Everyone who came to the ceremony stayed for the champagne reception, sit-down dinner and dancing. And because I had family and friends coming from the United States and England, having our guests spend the whole day together gave everyone the chance to get to know each other.
Some of our Belgian friends couldn't make it to the ceremony since it was on a Friday afternoon and they had to work, so they just showed up during dinner. I found that strange. In America, either you come to the wedding or you don't. You don't accept part of the invitation and you definitely don't skip the wedding ceremony itself. I'm pretty sure Emily Post would not approve, but then she's not Belgian.
I was used to thinking of the wedding ceremony as the most important part of the wedding and my job as guest was to witness and support the couple during this momentous and romantic event. Here, the ceremony is considered a boring formality, and the guest's role is to help celebrate afterwards. Perhaps this is because civil and Catholic weddings tend to be rather formulaic and impersonal, whereas we Americans put a lot of emphasis on customizing the wedding ceremony to reflect the couple's personality and beliefs.
It was everything I wanted our wedding to be, and it was perfect.