Definition - What does Windowed Mode mean?
Techopedia explains Windowed Mode
Some problems related to a windowed mode revolve around graphical displays. For developers who want to create a windowed mode for a program, understanding its effects on rendered graphics within the window is ultimately important. In addition to a loss of graphic quality, some programs can have issues with accessing memory to render the graphics correctly. All of this contributes to a common dialog between developers about how best to implement a windowed mode in various scenarios.