The Linux philosophy is to divide functions into separate programs. Windows combines the hardware-talking, the pixel handling and the window drawers and the look-and-feel layout all into one program.
Linux does the hardware-talking part of Windows
X-Window is the typical pixel handling
there are numerous window drawers, some small and fast, some complex and very configurable, you will hear about fluxbox, fvwm, Enlightenment and others.
The most popular look-and-feel layouts include a default window drawer, but as with everything in the Linux world, with a little or sometimes no effort you can substitute the one you want for the default. KDE, GNOME, XFCE do the look-and-feel layout
Linux is not a drop in replacement for windows.
There is something called GNU/Linux, this is all of Windows plus the word processor and other apps and utilities.