Skill consists of both the language and a one or more sets of functions. The Skill core functions can be found in the Skill Reference manual. Skill has an additional set of functions developed to support the Allegro back-end family of products whose names start with "axl". The axl functions can be found in the Allegro Skill Reference manual. This means to program in Skill with Allegro, you need the 2 Skill manuals (Reference and User Guide) plus the Allegro Skill Reference manual.
In your case, you are asking for the difference between interactive and general. This pertains to a single Allegro Skill function, axlCmdRegister, and has to do with how your Skill code registers itself as an Allegro command. Once your Skill code is registered as and Allegro command, you want your users invoke your code by the command name you register. Example, you create a Skill function called "myFunc()" that does something, you would register it via axlCmdRegister as the Allegro command mycommand". Users would then either type "mycommand" or you would add "mycommand" to the Allegro menu.
Typically, if you are going to change the Allegro database, you want to register your command as interactive. If your Skill code just displays infomation, you register it as general. General commands should not require user picks and will not terminate other interactive commands. When Allegro starts an interactive command it will first issue a "done" message to end any active interactive commands. The move and delete commands are both examples of interactive commands. The status form is an example of a general command.
Most commands should be written as interative. See axlCmdRegister for a complete description.