I’m learning about Views handlers and need some clarification on how its built.

Looking through the Views Bulk Operations module as seen below. There are 2 IF statements that checks for base table name and revision table. Now my questions are:

• When it says table, are they referencing to a table name in the database?
• title, group, help, etc… where can I find a list of other parameters for this as seen below in the screen shot?
• These fields show up when you click on the “add field” button in the View, but what dictates if it shows up in a content type or user type view?