The editor is built into every GTGameEngine game - it's a part and feature of the game. There is no need for a separate editor executable, but it is perfectly acceptable if it suits your development pipeline. When the editor is opened, the main game is paused, but still active in the background. The default shortcut for toggling the editor is Shift+TAB.

The editor is essentially a container for sub-editors. There is a sub-editor for most types of assets. Below is a screenshot with a few assets opened:

In the image above, we have two assets open: a model called "default.dae" and the sandbox intro scene called "intro.gtscene". You can switch between assets by just cycling between their tabs.

The panel on the left lists all of the assets in the data directories. This will automatically update when a change is made to the file system. For example, when you create a new model, you just drop it into the file system and the editor will automatically pick it up.

The tool bar along the very top will change depending on the asset that is currently showing. However, some items on the tool bar will be constant across all assets.

The bar along the bottom is currently only used for the command prompt. This will change in the future and will probably become something more of a utility bar for error notifications, a command prompt, etc. The command prompt is simply a place for you to call scripting functions which will run on the game's scripting environment.