According to uncle Wiki, a potluck is a gathering of people where each person or group of people contributes a dish of food to be shared among the group.
The word pot-luck appears in 16th century England, in the work of Thomas Nashe, and was there used to mean "food provided for an unexpected or uninvited guest, the luck of the pot". The sense "communal meal, where guests bring their own food", appears to have originated in the late 19th century or early 20th century US, particularly in the Western United States, either by influence from potlatch or possibly by extension of traditional sense of "luck of the pot".
You can read further explanation about Potluck here
The term potluck is quite common in Indonesia and sometimes we have potluck dinner at a friend's house. Potluck makes the host's life easier because the host doesn't have to cook the whole dishes for everyone.
In Australia there is a common expression called "Bring a plate". When you got an invite with note bring a plate doesn't mean that the host doesn't have enough plate hence they want you to bring a plate from home.
Bring a plate means to bring a dish of food to share with your host and other guests. Take the food to the party in any type of dish, not just a plate, and it is usually ready to serve. This is common for communal gatherings such as for school, work or a club. If you are unsure what to bring, you can ask the host.
You can find more common Australian expressions here