A focal point may mean the same as focus.
Elements of an antenna:
- driven element
- parasitic element.
The driven element is directly connected to the transmission line or source.
In mathematics, focal point has a meaning of a critical point of a distance function.
In terms of light and optics, the focal point is the point in which all the rays of light meet after passing through a convex lens, or reflecting off of a concave mirror.
