This is btw. a very important consideration when you are teaching literally anything.

Telling people to imagine a cone, then a plane, then rotating the other slightly and slice through the cone without touching the base, and then looking at a normal angle at the 2D shape of the resulting intersecting surface is a really good way to explain ellipses.

IF the person you're talking to can do all these steps. Turns out some people can rotate a cow in their head and some can't. If you cannot, a drawing or animation can help a lot to get the point across. Now I haven't gotten a problem with imagination at all, but I can only imagine how hard some subjects might be if you can't do that in your head.