According to Wikipedia, "a wedding reception is a party held after the completion of a marriage ceremony. It is held as hospitality for those who have attended the wedding, hence the name reception: the couple receives society, in the form of family and friends, for the first time as a married couple."
Since I moved back to Thailand in 2009, I've been to 3 wedding receptions - including one last night. They were all kind of the same concept meaning took place in a huge hotels' ballrooms, many guests were invited and many of those guests the brides and grooms might have met just once. By comparison; I'd been to many wedding ceremonies and receptions in the US, they were much more intimate - only close friends and families were invited. And usually the guests who attended the receptions came from the ceremonies, not just went straight to the parties.
If I ever have one of my own, I prefer the latter... that's all !