It is traditional in some cultures for the guests at bridal showers and weddings to receive party favors; these vary in price and durability in accordance with the desires and budget of the host or hostess. This practice has spread to many other formal occasions such as Baby showers, Engagement parties, Retirement parties, Anniversaries, and Holiday gatherings.
For small social gatherings such as birthday parties, guests may receive a simple and inexpensive favor such as a small toy. In some cases guests might receive a small "gift bag" with a handful of favors toys or trinkets, candy, pencils or other small gifts.
Occasions such as birthday parties, seasonal parties, unique events such as a Bar/Bat Mitzvah or Christening are a few social gatherings where favors may be appropriate.