The Position node outputs a vector of each point of the geometry the node is connected to.
The node can work on geometry domains besides points. In that case, the position data will be automatically interpolated to the new domain. For example, when used as part of the input to the Split Edges Node, the position for each edge will be the average position of the edge's two vertices.
For instances themselves, the output is the origin of each instance. However, if the node is for a geometry node that adjusts data inside instances, the position output of this node will be in the local space of each instance. See the Instance Processing page for more details.
Vector that indicates the location of each element of the geometry.