Jesus is in his final week on earth and each day we will find him teaching in the temple.  Using parables Jesus would teach important truths that he wanted to stick in the minds of those who heard them.  Here he describes a wedding, not just any wedding a Royal wedding.  It's a wedding to which the King has invited guests to come, sadly these guests all have an excuse for why they cant come and so they miss out.  But the wedding must go ahead and so in a remarkable turn of events the King fills the wedding with people who weren't just not invited they would never have been invited, they were sinners.  Jesus point is that those who respond tyo his invitation are blessed with his eternal presence, it is a serious thing to reject the invitation of the King.