Question

What are horizontal or vertical line graphs?

Answer 1

A horizontal has the equation `y=b` with `b` any constant number
A vertical has the equation `x=c` with `c` any constant number

A normal linear equation is mostly of the form `y=mx+b`
where `m` is the slope. In a horizontal graph, the slope is 0.
The `b` (called the `y`-intercept) tells you where the graph crosses the `y`-axis.

For the vertical graph a similar story goes and `c` is called the `x`-intercept.