Takes an Effex Grid Channel as input (which can be extracted by other nodes as a target channel)

Takes a Particle Property to use with the linked Channel.

Example Particle To Grid Emitter (P2G):
The P2G Emitter reads the Property link field and asks the particles if they carry this property. If they do the particle will return the value of this property and the P2G Emitter will emit this value into the defined Channel.

Used if no Property is linked. That way you can directly link a value to the defined Channel.
This value is also used as default value when a Property is linked but the particles do not contain such a property.