To re-size a window means to keep that window in its current position whilst altering its width and/or height. This is done by dragging (moving) the edges or corners of a window into its new width and/or height location. Only non-maximized (custom sized) and maximized (full desktop screen sized) windows can be re-sized simply because a window that is in Full Computer Screen mode occupies the whole of the computer screen whereby it has no re-sizable edges.
As you approach the left or right edge of a window the mouse pointer changes into the Left/Right directional pointer (Fig 1.0) and as you approach the top or bottom edge of a window the mouse pointer changes into the Up/Down directional pointer (Fig 1.1). These indicate that the window can now be re-sized (shrunk or expanded). Likewise. As you approach one of the corners of a window the mouse pointer changes into the Diagonal directional pointer (Fig 1.2) to indicate that the window can be re-sized in any direction (up, down, left, right or diagonally).
Fig 1.0 Move the pointer Left/Right
Fig 1.1 Move the pointer Up/Down
Fig 1.2 Move the pointer Any Direction
Moving the Up/Down directional pointer (Fig 1.1) either shrinks or expands the window's height whereas moving the Left/Right directional pointer (Fig 1.0) either shrinks or expands the window's width. Moving the Diagonal directional pointer (Fig 1.2) in any direction (left, right, up, down or diagonally) either shrinks or expands the window's width and/or height, depending on how you move the directional pointer of course. To re-size (shrink/expand) a window just follow the steps below.
Move the standard mouse pointer towards one edge or one corner of the window until the standard mouse pointer changes into a directional pointer. So in the example below (Fig 1.3) I have placed the standard mouse pointer over the right edge of the TextEdit application window whereby the standard mouse pointer has then changed into the Left/Right directional pointer (left/right arrows mouse pointer). At this stage it is very important to keep the Left/Right directional pointer's position steady, otherwise it will change back into the standard mouse pointer.
Fig 1.3 Position the mouse pointer over a window's edge so that it changes into a directional pointer
With the directional pointer steady; Click the left mouse button and keep it held down (clicked) whilst you then slowly move (drag) the directional pointer (physical mouse) either inwards (left and/or upwards) to shrink the window or outwards (right and/or downwards) to expand the window. So in the example below (Fig 1.4) I have moved (dragged) the Left/Right directional pointer (physical mouse) about two inches to the right, whilst keeping the left mouse button held down, therefore resizing (expanding/stretching) the width of the window by about two inches. When you have the desired window width simply release the left mouse button.
Fig 1.4 Click and hold down the LMB and then move (drag) the pointer until the window is of a desired width
To re-size the height of a window you do the same procedure as above but this time place the standard mouse pointer over the bottom edge of the window until the standard mouse pointer changes into the Up/Down directional pointer. From there you click and hold down the left mouse button whilst you then move (drag) the Up/Down directional pointer (physical mouse) either upwards or downwards. As soon as you have the desired window height release the left mouse button. In this next example (Fig 1.5) I am moving (dragging) the bottom edge of the TextEdit application window downwards in order to re-size the window's height.
Fig 1.5 Click and hold down the LMB and then move (drag) the pointer until the window is of a desired height
If you want to re-size both the window's width and height at the same time you can do so. This time instead of placing the standard mouse pointer over one of the window's edges you place it over one of the window's corners (any corner). In this next example I am going to re-size the TextEdit application window by moving (dragging) the Diagonal directional pointer (physical mouse) inwards (diagonally towards the top-left corner). You do not have to move (drag) the Diagonal directional pointer inwards. You could move (drag) it leftwards and then upwards for example. Either way will make the bottom corner of the window move inwards.
Fig 1.6 Click and hold down the LMB and then drag the window edges until window is of desired width/height
Fig 1.7 Release the LMB to apply the new window size
The above expanded the window's width and height for the example. However, in reality you might need to shrink two windows to equal size, side by side, so you can compare their contents. For example. You might have two text files open, side by side, so you can compare them and/or copy and paste text between their windows. Or you might need to shrink a window so it's not taking up too much space on the desktop screen but at the same you can still see its contents. These are the normal resizing scenarios.
Now take this scenario. You have the DOCUMENTS window (folder) open small. You then create sub-folders and files inside it, but cannot see the new sub-folders and files properly because the DOCUMENTS window (folder) is not big enough to view all contents (sub-folders and files). In this case you would have two choices. Either re-size (expand) the DOCUMENTS window (folder) or simply maximize it - Each time you maximize a window you can then restore it back to its original (smaller) size by clicking on its green MAXIMIZE (RESTORE) button (Fig 1.8 below) - This way you get the best of both worlds; You maximize so you can see all of the window's (folder's) contents and then restore back to a smaller (uncluttered desktop) window (folder).
Fig 1.8 Click on a window's MAXIMIZE (RESTORE) button to restore it back to its original (smaller) size
Fig 1.9 The larger maximized window (Fig 1.8) is back to its previous size
Shrinking, Expanding and/or Moving a window only can be tedious sometimes, but sometimes that is the only choice you have. And this is not just an Apple Mac experience, it's a computer experience. Meaning, you have to re-size and move windows around on a Microsoft Windows and Linux desktop screen too.