Step-by-step explanation
The general slope-intercept equation of a line is:

Where m is the slope and b is the y-intercept.
In this problem we have the function:

1) We see that the slope of the line is m = 0.
2) The linear function has a constant value y = 6 for every value of x. So we conclude that this equation corresponds to a horizontal line.
Answer
1) Horizontal
2) Slope: m = 0