This is the simpler of the two Environment Queries, as all it will do is return a list of all the TopDownCharacters within 1500 units of the AI then test if the AI can see the TopDownCharacters. If it can, then we'll get our ActorToFleeFrom for our Behavior Tree.
There are a number of ways this process can be done, each with their own advantages and disadvantages. Using EQS for this means that we can add additional tests at a later time to choose the best enemy (TopDownCharacter) to run from.
Some quick glossary terms you're going to run into:
A Generator creates Items in relation to a Context
Items are used in Tests often in relation to a Context (how far is Item X from Context Y)
Items are culled or scored based on the results of Tests