This because the line has no slope so the equation really looks like this if we were to follow the y=mx+b format.
y=mx+b y= 0x + b
because the number "0" multiplied by any value is still zero we can exlude that from the final equation of the line. In this case since m=0, the line is y=b.
b is the y intercept, or the value of y when x = 0.
