Where are the other foci of the parabola? My book writes that

Every conic section has four foci. Two are real and two are complex.

But during the discussion of parabola, it told only about one real focus. It only wrote that 

...the other focus and directrix lie at infinity.

So, what would the figure look like? I know it is difficult to visualize. But still I ask what will be the figure? Will it be an ellipse-like??? And what about the complex foci??? Please help.
 A: You obtain all four foci by constructing tangents to the conic through the ideal circle points $I=(1,i,0)$ and $J=(1,-i,0)$. In the case of a parabola, the line at infinity would be a tangent which passes through both $I$ and $J$. So If you intersect that tangent with itself, the point of intersection is not defined any more, while the other pair of focal points would be the points $I$ and $J$ themselves.
You can however consider a limit process which moves the conic from an ellipse to a parabola. In that case, the second focus would move towards the point at infinity where the parabola touches the line at infinity. So in another interpretation, that point can well be considered the second focus. This agrees with the physical observation that in an ellipse, light emitted in one focus will get reflected to pass through the other. In a parabola, light emitted atthe single focal point will get reflected to become a family of parallel light rays, so the point at infinity corresponding to this bundle of parallels is the second focus and incident with all these lines.
