In geometry, a locus is a set of all points, whose location satisfies or is determined by one or more specified conditions. In other words, the set of the points that satisfy some property is often called the locus of a point satisfying this property.
The concept of locus is fundamental in geometry. Suppose X and Y are two fixed points in the two-dimensional coordinate plane. If a point M moves on this plane in such a manner that its distance from the points X and Y are always equal, then the point M will trace out a definite path on the plane. Thus, a moving point M traces out a definite path on the given plane if it satisfies some specified geometrical conditions. Such a path traced out by a moving point M on a plane is called its locus. We shall learn more about the locus and theorems based on it. The set of all points that share a property, it usually results in a curve or surface. Example: A Circle is "the locus of points on a plane that are a certain distance from a central point".