Answer
The slope is $0$.
The $y$-intercept is $-1$.
See the graph below.
Work Step by Step
For a horizontal line, its equation's form is always the following:
$y=a$, where $a$ is a constant.
Here, the equation $y=-1$ is exactly as described above with $a=-1$.
Therefore the line is horizontal.
Recall that a horizontal line has a slope of $0$.
Every point that has a $y$-coordinate of $-1$ is on the line $y=-1$.
Therefore, the $y$-intercept is $-1$.
In order to sketch the line we can use the points $(0,-1)$ and $(1,-1)$.
Pliot the points then connect them using a straight line.
Refer to the graph above.
