it's a software, it works like Unity where you add C# code on the console or script. The difference is that NeoAxis has support and you can get the source code (AKA the entire program code) if you want to do something beyond for a price while Unity doesn't help you and Unity doesn't give you source code.
If you want something like NeoAxis mixed with Unity, look into https://www.stride3d.net/ it's 100% free, you can edit the source code and you can use Visual Studio.