[chbot] Discussion point ! Cell apps

[Marshland Engineering]

I have developed software for clubs which is now going commercial (if you call
$200 p/m commercial) 
The management software has been developed in Delphi and runs on PCs. The club
members interface with HTML and PHP code. 

I found PHP not best for coding and want to leave the management code in
Delphi. As it needs Internet access, the PC needs WIFI or similar. I then
though about using a cell with a custom app for some of the management
functions. 

That is where the problem lies. 6+ GB of Android Studio to run a "hello world"
app. 

Ok learning Java is an option for Android but what I would like to know a bit
more about is the overall structure of Android and maybe IOS operating system.
What are the underlying APIs, .net .whatever etc that are required to run
things on Android?  I was hoping that if I and maybe others have a fundamental
understanding of the whole platform, then making apps would be a bit easier.
Eg what is Glassfish and what do I need it ? 

Are there any simple IDEs for project developments. 
   
Cheers Wallace.