Reusing the current document window is a good way to minimize the number of windows open in your workspace. For example, if you are debugging a project and do not have the reuse option selected, you could have many windows open at one time. With the reuse window of current document option selected, you could have just one document window open.
If you chose the Reuse window of current document, if saved from the General options of the Environment category of the Options dialog box, the current document window functions as a browser where the contents a document window appears when you open it. Using the current document window as a browser does not affect the content of your document window. Each time a document window is opened, the document in current document window is closed. If you edit the contents of document while using the reusing current document window and do not save it, you will not lose your changes. Instead, when you open a new document window it appears in another document window and now you have two document windows in your workspace. You still have an opportunity to save the changes and close the previous document window.