VBS2 Light is a stripped-down version of the full version of VBS2, which is used by some customers (e.g. UK MOD or US Army) as a freely available training and marketing tool.
The main differences to the full version of VBS2 are as follows:
No real-time or 3D mission editor (only the old-style 2D editor is available)
Limited content (units/vehicles/objects/terrains)
No After-Action Review (AAR)
Limited MP player capacity
No HLA/DIS gateway (ability to connect to other simulators)
No ASI (ability to interface with VBS2 using C++)
No expansion/modding capability beyond the creation of user missions