There is a terminal window, owned by the OS. It has a minimize and a close button, for example.
Avi has an editor viewport, and this should take up the whole terminal window. (Someday it might have tabs and or splits. (Who knows what splits are actually called?))
There is a buffer viewport inside the editor viewport, where the thing you're editing is, and where you can type. You can move around there with hjkl and stuff. There might be more than one of these. (See tabs and splits, above.)
Also inside the editor viewport, below the buffer viewport, is a status line. That's where you probably see the filename you're editing in reverse text, when you're working in Vim.
Also inside the editor viewport, below the status line, is the command line. That's where things like :q or :sp README.md will appear.