Use the Accessibility Keyboard
The Accessibility Keyboard is an onscreen keyboard that lets you use your Mac without a physical keyboard. It provides advanced typing (such as typing suggestions) and navigation features that you can customize to make it easier to use your favorite apps.
When you use the Accessibility Keyboard, you can also turn on Dwell, which lets you perform mouse actions using eye- or head-tracking technology.
Turn on the Accessibility Keyboard: Choose Apple menu > System Preferences, click Accessibility, then click Keyboard. In Keyboard preferences, click Accessibility Keyboard, then select Enable Accessibility Keyboard.
Use the Accessibility Keyboard: Do any of the following:
Select typing suggestions: As you type, suggested words are shown. Click a suggestion to insert it in your text.
Adjust system settings: Click the system control buttons to adjust display brightness, sound volume, and video or music playback, or to access Mission Control and Launchpad.
Show or hide the Touch Bar onscreen: If your Mac has a Touch Bar, click the Touch Bar button
to display the Touch Bar across the bottom of the screen. Click the button again to hide the onscreen Touch Bar. For more information about the Touch Bar, see the Apple Support article How to use the Touch Bar on your MacBook Pro.Show custom panels: Click the Custom button
to display available custom panels. To return to the Accessibility Keyboard, press the Home icon 
in the top-right corner of the custom panel. Show alternate characters: Click Option, Shift, then a key. If an alternate character exists, such as à, it’s inserted in your text. Press and hold the key to show additional alternate characters.
If you often type characters with diacritical marks, it may be quicker to use dead keys (a modifier key pressed with another key to enter a letter with a diacritical mark). Click Option to highlight the dead keys, click a dead key, then a letter.
Change the Accessibility Keyboard: Click the Panel Options button
in the top right corner of the keyboard, then choose options to change the appearance of the keyboard, turn Dwell on or off, or set preferences. You can also customize the keyboard using the Panel Editor.Use Dwell with the Accessibility Keyboard: Click the Panel Options button
in the top right corner of the keyboard, choose Dwell, then choose an option. Or in Keyboard preferences, click Accessibility Keyboard, click Dwell Options, then choose an option. For information about the options, see Accessibility Keyboard preferences. Turn off the Accessibility Keyboard: Click the Close button
in the top left corner of the keyboard. Or in Keyboard preferences, click Accessibility Keyboard, then deselect Enable Accessibility Keyboard.
If you set the option to fade or hide the Accessibility Keyboard after a period of inactivity, you can make the keyboard fully visible again by moving the pointer over the faded keyboard or, if it’s hidden, moving the pointer.
You can use the Panel Editor to customize the Accessibility Keyboard for use with your favorite apps. For more information, see Use the Panel Editor.