From Wikpedia :  A constellation is any one of the 88 areas into which the sky — or the celestial sphere — is divided. The term is also traditionally and less formally used to denote a group of stars visibly related to each other in a particular configuration or pattern.

Some well-known constellations contain striking and familiar patterns of bright stars. Examples are Orion (containing a figure of a hunter), Leo (containing bright stars outlining the form of a lion), Scorpius (a scorpion), and Crux (a cross).

I think we're talking about the same thing, Ailsa.  I'll note that the Milky Way is actually a view of a portion of our own galaxy. Pretty spectacular under dark skies!!

Of course, when you say star system, I think of Star Trek, where the invincible Enterprise is always traveling from one system to another.  In that case, they're stars with planets around them, like our own Solar System.