The object on the right is a star, the one on the left is a quasar much more distant than the galaxy above. Without careful scrutiny, quasars appear as unresolved point sources -- i.e. like stars, hence "Quasi-stellar sources".
When an occulting disk is used to blot out the central source, the host galaxy for 3C 273 becomes visible.
Although the original definition of a quasar is "a star-like image", in practice this depends on the resolution of the observations. When HST looks at low-redshift QSOs of intermediate luminosity, it nearly always sees the surrounding "fuzz" of the host galaxy.