One end of the ramp is higher than the other. To get from the high end of the ramp to the lower you could descend to the tabletop through a vertical 'rise', then walk along the tabletop through a horizontal 'run'. The slope is equal to the 'rise' divided by the 'run'.
For example with one of the initial experiments, where a steel ball is rolled down a grooved track supported at one end by a stack of dominoes, the height of the stack is the 'rise', the horizontal distance from one end of the ramp to the other is the 'run', and the slope is the rise divided by the run.
If there is a ball or a cart on the ramp, then provided the ramp has sufficient slope, the object accelerates down the ramp. If the ramp is straight and there is no air resistance, the acceleration will be uniform. (Acceleration, as you should know at this point, is the rate of change of velocity with respect to clock time).
The steeper the ramp, the greater the acceleration.
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