Starting with console apps on Windows and Linux
Unarguably, console apps are the simplest type of application you can create in Delphi. All the code for an entire project can be contained in one unit; you don't have to deal with the nuances of any graphics engine, display framework, or even style. Of course, your user interface is quite rudimentary, but if your end goal is a server app deployed to a headless machine such as a remote Windows or Linux server, then this is the perfect starting point.
As a quick review, to create a console app in Delphi, select File | New | Other from the main menu and select Console Application. This creates a simple program that does nothing more than trap an error. Add a couple of lines of code between the try and except lines that were provided for us:
begin
try
Writeln('Hello from Delphi!');
Readln;
except
on E: Exception do
...