Focus of a Parabola

The focus of a parabola is a fixed point inside the parabola. The distance of any point of the parabola from its focus is equal to the distance of that point from a fixed straight line called the directrix of the parabola.

The focus of a parabola always lies on its axis, that is, on the line about which the parabola is symmetric and passing through the vertex. The focus never lies on or outside the parabola.
Focus of a parabola
Each parabola has its own focus. The coordinates of the focus can be determined from the equation of a parabola as explained in this post.