The simplest way to distribute a game for PC is to copy the executables (godot.exe on windows, godot on the rest), zip the folder and send it to someone else. However, this is often not desired.
Godot offers a more elegant approach for PC distribution when using the export system. When exporting for PC (Linux, Windows, Mac), the exporter takes all the project files and creates a "data.pck" file. This file is bundled with a specially optimized binary that is smaller, faster and lacks tools and debugger.
Optionally, the files can be bundled inside the executable, though this does not always works properly.