For $19.99 USD you'll get both the US Forces and the Oberkommando West factions for Company of Heroes 2. As stand-alone additions to the game these factions will give you access to the CoH2 multiplayer experience, without requiring you to own the base game.
For pre-ordering you'll get the following bonus content:
• 2 new vehicle skins (1 per faction) - applicable to all weight classes
• 2 faceplates (1 per faction)