"Point out" and "point to" have substantially the same meaning, but, idiomatically, "point out" usually refers to a more abstract or complex object whereas "point to" refers to a more concrete one....
A locus of points is just the set of points satisfying a given condition. The locus of points equidistant from a point is a circle, since a circle is just a set of points which are all the same...
Each is distiguished by a phase change(solid to liquid, liquid to gaseous, etc.) though there is also an amount of energy necessary to cause that change even at the same temperature.
