I'm a student pilot working on my PPL and I just did my first solo cross country earlier today. While I was on flight following I received a call from approach that sounded like "N123 traffic 4 miles north of the ____ intersection indicating 1000 maintain VFR". I just read back "Maintain VFR N123" as I was a little bit lost on what they were talking about. After some research I now kinda know what intersections are but I had literally never heard of them and in my case it wasn't plotted by name on a sectional. What exactly do I do in this situation? Do I just tell the controller I don't know where that intersection is? Is it common to receive traffic advisories relative to intersections?
I would tell the controller that I don't know where that intersection is.
In my experience, I would not expect ATC to issue a traffic advisory to a VFR aircraft in relation to a stand-alone IFR intersection.
However, in the U.S., note that on Sectional Charts some IFR airways are depicted in blue and some IFR intersections are shown.
But, if I was not able to quickly identify the position/intersection where ATC indicated the traffic was located, I would advise them of this and request to receive the traffic information in relation to my position, as opposed to the traffic's relation to an IFR intersection.
Below, is an example of an IFR Intersection named "DARTS" that is located within (depending on altitude) the Burbank, CA. Class C airspace depicted on a Sectional Chart. However, again, it would be very unusual for ATC to issue a traffic advisory to a VFR aircraft in relation to an IFR intersection. If this should happen I would immediately advise them and ask for the location of the traffic in relation to my position.
(The emphasis red line and red circles on the images below are mine)
As a final note, the Sectional Chart below covering an area near St. Louis, has a combined IFR Intersection and VFR Waypoint named "FASHE." It's possible, for example, if ATC has instructed me to report FASHE (the VFR Waypoint), prior to receiving a clearance into the St. Louis Class B airspace, they might issue a VFR traffic advisory referencing the "intersection" named "FASHE" because it is also a VFR Waypoint. I don't know how likely it would have been in your case, but it's something to consider anyway.
Every time when something in communications is not known to you as a student pilot you should admit it and report to the ATC, especially when it is a time pressured nature. Most likely what happened in your case is that air traffic controller simple "forgot" that you are VFR flight (controllers are humans too). I always tell my students to advise controllers that you are a student pilot, for example on the solo cross-country. Although not 100% but most of the time you'll be treated with "extra care". You need to do it only in the beginning of the flight because when you switch controller handover will already have "student pilot" in the comments. As the previous poster suggested the best was to say that you do not know where the waypoint is located and ask to clarify the location of traffic.