How does a conditional work (the 88 thing)?

An example of a conditional would be:

05 STORE-CODE PIC XX.
88 BOSTON VALUE 01.
88 NEW-YORK VALUE 02.
88 TORONTO VALUE 03.

In this example, when you get down to a usual IF statement, without using a conditional you might say something like:

IF STORE-CODE = "01"

However using a conditional, you could do the exact same thing by typing:

IF BOSTON

This makes a lot easier when it comes to ever yes/no questions in a program or where there is a long list of different options (easier to create a name for each option versus remembering/writing down the values and what they mean).