In addition to the bride and groom, traditional weddings involve a lot more people. Typically, these positions are filled by close friends of the bride and groom; being asked to serve in these capacities is seen as a great honour.
For the couple:-
Ringbearer - an attendant, often a young boy, who carries the wedding rings.
Ushers - helpers, usually men, who assist with the organization.
For the groom:-
Best man - a close male friend or relative of the groom, given a place of honour.
Groomsmen - one or more male attendants who support the groom.
For the bride:-
Maid of honour - a close female friend or relative of the bride, given a place of honour. If she is married, she is called the "matron of honour" instead.
Bridesmaids - one or more female attendants who support the bride.
Father of the Bride - One who symbolically "gives away" the bride. If her father is deceased or otherwise unavailable, another male relative, often an uncle or brother, will give the bride away.
Flower girl - a young girl who scatters flowers in front of the bridal party.
Junior Bridesmaids - young girl typically between the ages of 8 and 16 who is too old to be a flowergirl, but the bride wants to be a part of the wedding.
Wedding guests are generally sent invitations to which they are expected to reply (rsvp). The guests are generally invited to both the wedding and the wedding reception afterwards, although sometimes reception places are limited. Often certain people are invited due to perceived family obligations, as to not receive an invitation can be considered an insult.