Wedding reception is like the celebration after a wedding.
Sometimes, if a couple goes to... say... Las Vegas for a wedding, they might come back to their general area, say... New York and have a reception so that their family around that area can be a part of it.
Sometimes, receptions follow directly after a wedding... like a party
More information:
# a reception for wedding guests held after the wedding
wordnet.princeton.edu/perl/webwn
# A wedding reception is a party held after the completion of a marriage ceremony. Some sort of post-marriage party is traditional in most societies around the world, but with considerable variety on the details.
en.wikipedia.org/wiki/Wedding_reception