a piece / slice / share of the pie

What is the origin of the idiom "a piece of the pie" and when to use it?

The idiom "a piece of the pie" is believed to have originated in the United States in the mid- to late-1800s. Its origin is thought to be related to the division of land or resources, where a pie was seen as a metaphorical representation of a limited resource that needed to be divided among multiple parties. The usage of the idiom has since expanded beyond its original context and can now refer to any situation where there is a limited resource or opportunity that needs to be shared among multiple parties.