Troops are the hart and life blood of an army. The main way that this manifests in Warhammer 40k is that usually only troop units can capture and control objectives. This means that you have to have enough troop units at the end of the game to control the objectives, or else all you hard work is in vain!
The Chaos Space Marine army has 2 troop choices as standard, the Chaos Space Marine units and the Chaos Cultists. These 2 options are often expanded to include one of the Elite unit types depending on the HQ choice that you pick.
Chaos Space Marines
The Chaos Space Marines are the Chaos corrupted version of the Imperial Space Marine. This means that if you are familiar with the standard Space Marines then you will be able to adapt to the Chaos Space Marines quickly.
Know no Fear? Oh yes they do!
The main difference that you will come across if you are moving across from the Imperial Space Marines to the Chaos Space Marines is that you loose the ‘ And they know no Fear’ special rule.
In practical terms this may mean that you will need to take more pinning and moral tests. However you should find that their LD9, and LD10 for the Aspiring Champion will mean that you will pass leadership tests most of the time.
Is that all there is?
You may be thinking that this seems a short list for troop choices, specially is you have been using the 2007 Codex: Chaos Space Marines rulebook. Well you can still use some of the Elite choices depending on the HQ choice you take, and the upgrade options you take for them. There is more about this in the Chaos Space Marine Elite Tactics section.