What are the variables in stem and leaf plots?

There are normally 2 variables, a discrete variable which is a variable which can only take a certain amount of things, for example a jar, car parking lot. A continuous variable is a variable which obviously varies and can have an infinite amount of values attached to it.

in geometry, parallel lines are lines in a plane which do not meet; that is, two lines in a plane that do not intersect or touch each other at any point are said to be parallel. by extension, a line and a plane, or two planes, in three-dimensional euclidean space that do not share a point are said to be parallel.