The slope-intercept form of a linear equation is .
Move slider . See the steepness of the line change. The slope of the line is .
When is negative, the direction of the line changes. When , the line is flat.
Vertical lines do not have a slope.
Where the line intersects the -axis is the -intercept point of the line. The -intercept is the point .
Only the is used in the equation, and it is the constant term of the equation.
Move slider . See the line move up or down.
When is positive, the y-intercept is above the -axis.
When is negative, the y-intercept is below the -axis.

To remember the different meaning for different slope values:
It is easy to walk across the flat ground. When , it is like flat ground.
Some climbs are barely hills, some are challenging hikes, and others require major planning and safety gear.
When , the climb is barely a hill.
When , the slope is 45 degree from the -axis and is a challenging hike.
When , the line approaches the -axis and becomes a major climb requiring planning and safety gear.
Only dare devils would scale the side of a skyscraper. The steepness of a vertical line is akin to scaling the side of a skyscraper. The slope does not exist.