Question

What does the graph of x = -1 look like

Answer 1

Vertical line.

Answer 2

All it's saying is (-1,0)

Answer 3

It's saying more than that, @kelsey1 , unless you're only assuming one-dimensional graph.
In two dimensions it's a line. In three dimensions, it's a plane.

Answer 4

I added on to what you said with the vertical line.