What it is
A Vector3 is three numbers fixed when the world is built. The node that uses it decides whether it means a direction, a position or an offset.
Also accepts
These types plug into a Vector3 input and convert on their own:
Made by9
Used by9
Good to know
One number fills all three
Plugging a single number into a Vector3 input sets X, Y and Z to it. To set only one part, use Combine XYZ.
Length
Vectors keep their length. Use Normalize Vector when you need a unit direction.