Hello, my booster pump is leaking from the area that is circled (not sure what it is called). No matter how much I tighten it, there is no seal between the part thats connected to the hose and the part that says hand tighten only. Any suggestions? Thank you. 
That pump looks brand new. Is it? That is the union nut fitting where water comes out. It should have an O-ring in there to help seat it against the top of the outlet fitting. You might want to check to ensure the O-ring is there and perhaps give it a light coating of pool lobe (NOT petroleum jelly).