Identify the variables. Occurrences involve variables. Weather is an occurrence, but rain is a variable, sunshine is a variable, and snow is a variable. The heights of adult maple trees are occurrences, but the individual heights are variable. The flip of a coin is an occurrence, but the head and the tail are variables.
Chart the occurrences. If you are studying fatal automobile accidents, then you can use a number or a bar graph or some other mathematical representation to chart the occurrences. If you are studying five separate counties, you can establish a distribution of numbers based on this geographic division. Over time, you can establish a ratio of fatal automobile accidents to total automobile accidents, and that ratio may be different for each county.
Determine whether the variables and/or distributions are continuous or discrete. There are many different kinds of variables and distributions. All, however, are either continuous or discrete. A discrete variable can be any number of occurrences between zero and infinity, but it must be a whole number. There can be 100 fatal accidents, but not 100.3 fatal accidents. The accident is either fatal or it is not. You can get 50 out of 100 coin tosses to turn up heads, but there is no such thing as 50.5 heads. This is a discrete variable.
If you are measuring the heights of adult maple trees in Adrian, Michigan, however, you will have a fixed number of maple trees, but the heights can range in infinitely smaller increments between zero and infinity. You can continually divide the potential heights without end. So this is a continuous variable.