Locus :-
If a point travels according to the given condition then path created by point is known as the locus of that point.
Or locus is a geometric shape where every point satisfies the given condition.
Equation of the locus:
A algebraic relations got from the geometric condition for any variable point (x,y) is known as equation of the locus.
Example:-
Find the locus of a point, which is always at equal distance from two points (-1,2) and (4,0).
Let the coordinate that point is P(h,k).
Now according to the given condition
Distance from p(h,k) to (-1,2) = distance from P(h,k) to (4,0)
So locus of point p(h,k) is