You can realize probability as the relative area between a figure and an interesting part of that figure.
For instance, if you have a calendar of last year, and you marked all the days where it rained in blue, the probability during the year that it will rain is defined as the number of blue days to the number of days total
But different months rain different amounts. If we look only at the month of April, likely more will be blue that month than on any other month.
Conditional probability here would be linked to looking only at the month of April.
The total probability, then, is the number of days it rained (days marked in blue) and the number of days it didn't (not marked) added together, divided by the number of total days. Of course, there are 30 days in April, and hopefully each day, it either rained or it didn't rain, since any other possibility would be hard to imagine.