Layers

Layers - Sandbox2 Editor

Sandbox uses layers for two main reasons: Organizing your Level Content and Streaming Performance.
Any object you place on a layer (vegetation/terrain excluded) can be hidden/unhidden via the Layer Control and also via Flowgraph, which allows loading/unloading of level areas to keep performance high and memory consumption low.
More information concerning Using Layers can be found here: http://docs.cryengine.com/display/SDKDOC2/Using+Layers
Every 2D, 3D artist understands the concept/power of Layers. Basically, layers are the computer equivalent of tracing overlays on a drawing board.

First Layer
The first time you create a map the editor will create a Layer named 'Main', it is up to you to create every Layer after that.
If you do not create any other layers then all of your work will confined to Layer 'Main'. On a very detailed map this will slow down the process considerably seeing how everything is loaded into memory.
There are 5 buttons on the RollupBar - Layers is at the far right. (only 5 buttons must mean it's important)
Layers Advantages
Utilizing layers allows you to isolate different items used in the map. Layers allow you to collaborate with others. Let's say you are working on the terrain in your editor, another person can be working on a base in their editor. Layers allow you to hide items in a congested area making item selection while editing an object much easier. Layers allow you to take a map you designed say for TC (Terrain Control) and convert it for TSA (Team Solaris Arena) map just by turning off certain layers. You can set up a development layer say Measurement for lines to establish gameflow parameters then when you are done just Hide the layer before Exporting the game for play.
Layers can be named anything so give your layer name meaning like; Roads, Trees, Bridges, Decals, IS_HomeBase, Clan_HomeBase, Capture_PointA, Sounds, Music, etc. Layers makes working with maps much more efficient. Layers have so many uses, make them an everyday habit.