From the Introduction:
This is the boiled-down "essence" of GURPS
: all the fundamental rules, but not the options and embellishments that often confuse new players. Once you're comfortable with these rules, you can pick up the GURPS Basic Set
and jump right into the action. Experienced GMs will, we hope, find this a valuable tool for introducing new players to the game.
This is a distinct version of the GURPS Lite document specifically designed for GURPS WWII (and styled in a more militaristic format). It strips out the parts that aren't relevant and expanding the areas that are more useful for a WWII campaign (including a more detailed list of social traits, and tailored dis/advantages, skills, equipment, and rules section).