PSD-95 is a protein located in the post-synaptic region inside a cell. In fact it's named for this, "post synaptic density-95" referring to the dense appearance of the post synaptic area on an EM microscope and this protein's presence there.
"Synaptic targeting" in this context refers to how that protein gets to where it belongs (the synapse) in the cell, rather than just floating around in the cytoplasm by simple diffusion.