Suppose, for example, : Find the locus of point P that is 6 cm from point C.
Now, see that,
All the points that are 6 cm from C make a circle.
these points lie on a circle with a radius of 6 cm.
Please see diagram
Determine the locus of points equidistant from two points A and B
Let us make two circles with centre A and B and equal radius of AM = BM
so, point M is at equal distance from A and B.
change the distance AM = BM and make another circles keeping same centres.
so, the points of intersection of two circles give a line, which is locus (red dotted line in diagram).
A locus is a set of points satisfying a certain condition.
A locus is a path. The path is formed by a point which moves according to some rule.
For e.g. If you want to find the locus of a point A lying 1 m away from a given point B, the locus is a circle of radius 1 m, with centre B. That's because A can lie 1 m away from B in any direction, and a circle is that path (locus) which fully describes where A can lie.
I hope that helps.