Linear Relations - Line or No Line?
If you were to graph the number of pop cans sold at a family garage sale, you wouldn't connect the dots because this is discrete data - you can't sell part of a can, so you only have data on whole numbers of cans.
(After pressing the Zoom Out button)
But if you were to graph the number of cans sold in your town in a day, or across the country in a year, at some point the dots become too close together to graph as points, so you draw the line. This is still discrete data, but because of the scale of the graph you draw it with a line instead of dots.