So far our programs run straight down the page. Real work needs decisions: do one thing in one case, something else in another.
A decision starts with a question the program can answer with true or false: is this total greater than that limit? is this value equal to that word? These are comparisons.
You act on the answer with If and Otherwise. The lines indented under If run only when the question is true; the lines under Otherwise run only when it is false. The program below sends an invoice down one of two paths depending on its size.
Run it with the total at 15000, then set it to 500 and run again. The program takes a different path each time.
Takeaway
A comparison produces true or false; If and Otherwise turn that answer into a choice. This is the heart of every rule a business runs.