It's a full engine! It specializes in 2D games but their 3D support is growing rapidly, just not up to what Unity and Unreal offer right now. Here's a showreal they did for games released using Godot last year: https://youtu.be/UAS_pUTFA7o?si=QuPq6hByt-lve-vg

Godot is a full engine, I would position it in the market somewhere between Unity and GameMaker Studio. It is capable of making 2D and 3D games, though there's some things Godot lacks, for example the asset streaming capabilities that allow for large seamless open worlds without loading screens, they're working on that.

Godot runs on WIndows, Mac, Linux various BSDs, and they're working on an Android port. Godot games can be exported to Windows, MacOS, Linux (and thus SteamDeck), BSD, Android, iOS and the web. Godot games can be ported to consoles, but Microsoft, Sony and Nintendo are really fucky about licensing. The way you would go about publishing your Godot game to Playstation, Xbox or Switch is to work with a porting company who specializes in such things.

Fun fact: The Godot IDE is itself a Godot "game." The Godot editor runs in the Godot engine and is built from UI tools available to end users; this makes it pretty easy to create tools and extensions to customize the editor to your team or project's needs. It's also a practical demonstration of how robust Godot's UI creation tools are; I've been toying with the idea of building a woodworking CAD program in Godot.

I have literally no idea. It just pops up left right and center so it seemed it is a competitor.