its information on how to play Warhammer
this manual will tell you about the rules of the game of Warhammer 40,000 there is a book that is called a codex there you will be able to find the statistics and amount of points that different kind of units have,how much damage and the creation of that unit. However the statistics change every 3 years. There are a lot of different armies that represent different kind for example you have the imperium of humans that consists of: Space Marines, Space Wolves, Blood Angels, Dark Angels, Astra Militarum, Adeptus Mechanicus, Ultramarines, Gray Knights, Deathwatch and some other minor sections. There are also traitors of humanity and those are Chaos Space marines, Death Guard combined and Thousand sons with monsters that prey the demons like Chaos Demons. And you have other different creatures and factions that you can play with like: the Orks, Tau Empire, Tyranids, Necrons, craftworlds and the Drukhari. Every single army has their own strengths that you can see in the codex A good example would be that the Astra militarum have superior fire power over the Tyranids that don't use much of range equipments and would not be able to compete in it with the Astra Militarum, but when it comes to close combat Tyranids have a large variety of monsters with different strengths that outclass the Astra Militarum because they have fewer close combat weapons.