When I open my attribute table, click on a column, and select Field Calculator it opens and doesn't list all of the Fields in my attribute table. Why can't Field Calculator find these Fields?
If you have hidden fields in the attribute table, then they will not show up in Field Calculator. In the attribute table, go to
Table Options, and then
Turn all Fields On.
The key to note here is "in other dialogs". If you hide them here, they will be invisible to most other tools, identify, export, etc.