It's party where two people get married
Wedding party
It's a party to celebrate the day when someone was born
Birthday party
It's a party where people dress up as characters (like for Halloween)
Costume party
It's a party to celebrate an engaged couple and their upcoming wedding.
Engagement party
It's a party to celebrate someone's moving into a new home
Housewarming party
It's a party where people celebrate the last day of the year
New year's Eve/ Year End Party
It's a party to welcome back someone who has been away for a long time
Welcome party
It's a party to say goodbye with people who are about to leave a company or start a long journey...
Farewell party
A formal event at which students receive a certificate for successfully completing a course of study
Graduation party