The concept of buffer and window in Emacs can be confusing to new users: the terms are used to mean different things in Emacs than in other tools. (See for example this question.)
The Emacs Manual provides details about using multiple buffers.
To answer the specific question: many buffers can be open at one time in Emacs, and you can freely switch between them without having to minimize or kill anything. You can simply switch to another buffer by name (
C-x b) or choose one from the list of open buffers (
C-x C-b). As mentioned in the comments you can also use
bury-buffer, which moves the buffer you are currently looking at to the end of the list of buffers and shows you the next one. You can split the frame in to several windows and display a different buffer in each one... There are many options.
If you are a new Emacs user I would suggest going through the Emacs Tutorial, which covers the basics. You can start the tutorial in Emacs using
C-h t (control h, followed by t).