Use
You can use earmarkings to assign the budgets of budget structure elements to an organizational unit, or to a position. This means that, on the basis of your system settings, you can only use the earmarked budget to finance the organizational unit or position in question.

This means that, when you are financing persons or positions, you can use earmarkings to select the budgets structure elements that are allowed for the persons or positions in question.
If you assign funds using the budget of a budget structure element that is earmarked for a different organizational unit or position, the system issues a message telling you that you are violating an earmarking.
Prerequisites
In Customizing, you must have specified how the system should react if an earmarking is violated (step: Overall budget ® Settings for Financing Persons/Positions ® Define System Reactions for Financing).
You must already have defined an organizational structure.
Features
You can create an earmarking between a budget structure element (and, consequently, its budget) and an organizational unit or position.
If you define an earmarking for a budget structure element, this mean that the system assigns the budget proposed for this budget structure element to a specific organizational unit or position, and uses this budget to finance the organizational unit or position in question.
See also:
Creating an Earmarking Editing Earmarkings