Volumes are invisible areas that are created to help the game developers perform a certain function. They are used in conjunction with the objects in the level to perform a specific purpose. Volumes are commonly used to set boundaries that are intended to prevent players from gaining access to trigger events in the game, or use the Lightmass Importance Volume to change how light is calculated within an area in the map as in Chapter 2, Creating Your First Level.
Here's a list of the different types of volumes that can be customized and used in Unreal Engine 4. But feel free to quickly browse through each of the volumes here for now, and revisit them later when we start learning how to use them later in the book. For this chapter, you may focus your attention first on the Trigger Volume, as we will be using that in the later examples of this chapter.