Locus from two perpendicular lines

In geometry, a locus (Latin for “place”, plural loci) is a collection of points which share a property. For example a circle may be defined as the locus of points in a plane at a fixed distance from a given point.

A locus may alternatively be described as the path through which a point moves to fulfill a given condition or conditions. For example, a circle may also be defined as the locus of a point moving so as to remain at a given distance from a fixed point.

Will you consider the set of points traced by point I in the GeoGebra applet below a locus? What property do they share?