If your screen is big enough, it is best to avoid making windows fill the screen. If you use windows instead of full screen, you can more easily move between different tasks and that makes multi-tasking far simpler.
If you are unsure about whether what you are looking at is full screen or a window, look at the top right corner of the window. There should be three buttons there. The middle one gives you this answer. If it is a single square, you are looking at a window. If it is two squares, you are looking at a full screen display. You can switch a full screen display to a window by clicking this button. It is a toggle – like the light switch on your wall.
You can change the size, shape and position of a window. Use your mouse. When you move it to exactly the edge of the window, the arrow will change shape. If you hold down the mouse button you can drag the edge. This works on any edge or any corner which will change both dimensions at the same time.
You can move a window by pointing at the title bar at the top of the window and holding the primary button and dragging it. These methods do not work on a full screen display.
When you move a window near the edge of the screen, the action that initiates the Aero Snap feature is when the mouse pointer contacts the edge of the screen. You can disable this feature.
Open Control Panel / Ease of Access Center / Make the Mouse easier to use.
Place a check mark in the Prevent Windows from being automatically arranged when moved to the edge of the screen option.