Hi,
I am getting to know blueprints by doing the tutorials, the tutorials are helpful but they don’t list what the node for the variation in the vector. I have posted it below, i think it varies the vector that it is given.
Tutorial image: https://docs.unrealengine.com/latest/images/Engine/AI/BehaviorTrees/QuickStart/11/fullGraph.png
Still pretty much a novice myself, so if anyone can correct me, please do!
I think the node itself is used to add a value(s) to an existing vector.
I’ll try to explain by using the gyazo picture as an explanation:
Say the actor’s location is dead center (0,0,0) and you want to trace for objects between the actor and a certain distance and direction.
You use the actor’s location as a starting point (still 0,0,0).
Then you need an endpoint. To do this you use the unknown node(I think it’s called "vector+vector).
You add the location of the actor as one value, then you add what needs to be added to get the location of the endpoint of your trace.
In this case you add 15.0 to the direction of z. The trace node now knows to only trace everything between the actor (0.0.0) and the endpoint (0.0.15).
Hopefully this explanation helped you out somewhat!
Rustywaffles is correct 
The node is called ‘Vector+Vector’ and it’s just a maths operation. They’re also available for other variables with numeric values e.g ‘Float+Float’, ‘Integer+Integer’.
As a vector is made up of 3 values; X, Y and Z, when you use the ‘Vector+Vector’ node you can choose how much you want to add to each of the X, Y and Z values which affect the position in space.
So if you started with a vector (5, 5, 5) and connected that to the first pin of the ‘Vector+Vector’ node, then typed in values into the spaces on the ‘Vector+Vector’ node, say (10, 10, 10), then the resulting vector will be
(5, 5, 5) + (10, 10, 10) = (15, 15, 15).
So the position of the first vector has been shifted +10 units in X, +10 units in Y and +10 units in Z. It’s resulting position is now at (15, 15, 15).
You can also connect a Vector variable to the second pin of the ‘Vector+Vector’ node if you want to add together two vectors that you already have stored. For example say you had already set two Vector variables (5, 5, 5) and (5, 10, 15). Connect the first vector to the first pin, and the second vector to the second pin you’ll get
(5, 5, 5) + (5, 10, 15) = (10, 15, 20).
Also hope this helps clear things up a bit
