A window used as a scratchpad area where fragments of Smalltalk code can be entered, stored, edited, and evaluated. (Inside Smalltalk, vol I, p. 71)
In Pharo the workspace is called "Playground". A workspace is a place to quickly try out code snippets and thus develop code which later might be copied to instance or class methods.
To open a workspace window in Squeak, one possibility is to bring up the World menu, select "open...", and then select "workspace".
You can then type in any Smalltalk code inside the workspace window and execute it or inspect it.
This is normally done by typing in some code, highlighting it with the mouse, and then selecting "do it" or "print it" or "inspect it" from the pop-up menu. Or "debug it" to open a Debugger on the code. (To bring up a pop-up menu in Squeak, use the "yellow" mouse button, normally the middle or right mouse button, or option-click on a Mac. Or you can use the menu shortcut keys, such as cmd-d, alt-p, etc.)
For example, if you type 3 + 4 in a workspace, highlight it, and select "print it" from the pop-up menu, it will print the result 7. You can type any small or large piece of Smalltalk code...