A wedding toast is a certain kind of rite performed at weddings to honour and celebrate the couples who have just been married. It is typically an expression of goodwill.
Usually, the best man toasts the bride, the chief bridesmaid toasts the groom then the father of the bride or chief patron of the wedding toasts the couple.
The significance of a wedding toast is to wish the new couple well and also to entertain and amuse the guests.
The clinking of glasses comes from the middle ages when ringing a bell was a way of warding off evil spirits that were against the couples union.
Depending on how religious the newly wedded couple, they might have a spiritual leader make a speech and give pre-nuptial blessings.
Sources: Wikipedia and WeddingSpeech