Among Jews of a previous generation, it would be used to mean a Jew from the same village, city, or region, depending on the context. In the United States, it is often used to refer to another Jew. Many Jews today may not know the term, but they play the game anyway. It is particularly delicious to find out that someone who is famous, but is not obviously Jewish, is Jewish.
Some people call it finding members of the tribe.
I personally like the old fashioned term. Playing LTL is a little less interesting today than it was a generation ago when Jewish actors had to change their names to be acceptable to the general public. Or that was the perception that mostly Jewish-run film studios had. Kirk Douglas is Izzy Demsky, Tony Curtis is Bernie Schwartz, and so on. In fact, until thirty years ago, one would be hard-pressed to find a major Jewish actor or actress who did not change their name.