Dealing with the security situation in Afghanistan is explained a number of ways. The simplest descriptions come from newspaper headlines and politicians. The shortest version that makes sense to most people is, "assist the Afghans to provide security for themselves." There are increasingly more complex descriptions, which go into detail about who the various hostile forces are (Taliban, al Qaeda, other Islamic radicals, drug gangs), and what characteristics weaken both the hostiles and the government supported by NATO.
These descriptions get increasingly more complex when you get your information from American military and intelligence organizations. An example of how complex this can become is available here .
This kind of analysis makes more sense when used in a simulation, where the various components can be seen having a cause and effect on all the other components. Think of how a complex spreadsheet works. These are usually put together as simulations, which you can play with, to see the cause and effect relationships of all the "actors." Alas, these sims are highly classified, like a football teams playbook.