More information about Magnifier from support.microsoft.com:

Windows 10

Magnifier is a tool that enlarges part—or all—of your screen so you can see words and images better. It comes with a few different settings, so use it the way that suits you best.

Open Magnifier

To open Magnifier on a keyboard, press the Windows logo key‌  and + (plus sign). To open it by touch or mouse, go to Start , then Settings > Ease of Access Magnifier, and then move the slider under Magnifier to turn it on.

Magnifier opens in full-screen view unless you change the settings.

Close Magnifier

To exit Magnifier, press the Windows logo key  + Esc or select the magnifying glass icon  , and then select the Close button on the Magnifier toolbar.

Change Magnifier views

With a mouse, you can use Magnifier in three different view: full-screen, lens, or docked. Try them all to find out which one you prefer.

In full-screen view, your entire screen is magnified. You probably won’t be able to see the whole screen at the same time when it’s magnified, but as you move your mouse around the screen, you can see everything. If you have a touchscreen, Magnifier will display white borders around the edge of your screen. Drag your finger or mouse along the borders to move around the screen.

In lens view, when you move around the screen, it’s like moving a magnifying glass around.

Docked view works on the desktop. In this view, a magnifier is docked to a portion of your screen. As you move around the screen, parts of the screen appear magnified in the docking area, even though the main part of the screen is unchanged.

Customize Magnifier

Change the way Magnifier works by using the zoom buttons (

Zoom in button

and 

Zoom out button

) to enlarge or reduce your screen. Or press the Windows logo key  and + (plus sign) or the Windows logo key  and – (minus sign) to zoom in and out.

  1. Open the Magnifier options button
    Magnifier options button

    to make changes to the level of zoom, color, or focus.

  2. Press the Windows logo key  and + (plus sign) to open Magnifier.
  3. On the desktop, select the Magnifying glass icon , and then select the Options button 
    Magnifier options button

    .

  4. Do one or more of the following:
    • Use the slider to choose a zoom increment. The percentage you choose here will be the increment by which Magnifier enlarges the screen when you press the Zoom in button 
      Zoom in button

      .

    • Select Turn on color inversion to reverse colors on the screen. Sometimes reversing colors can make text easier to read.
    • Select a check box to choose how Magnifier focuses. Magnifier can follow your mouse, the insertion point, or the keyboard.

Use Magnifier with a touchscreen

Perform a variety of tasks on a touchscreen with Magnifier:

  • Zoom in and out by tapping on the corners.
  • Move around the screen by dragging along the borders.
  • See where you are on the screen by tapping with two fingers on opposite borders.
  • Exit Magnifier by tapping the Close button.