Doing so will cause the Dock to disappear, allowing you to use that space for whatever else you're working on. When you want to use the Dock, you can simply move your mouse pointer over the spot on the screen where it used to be, and it will pop up.
You can also get a little more space by hiding the menu bar. Within System Settings, go to control center Settings, then Set Hide and show the menu bar automatically option of Always,
This will hide the menu bar at the top of the screen in the same way you hid the Dock before. Now, obviously, this gives you less space than hiding the dock, and some people won't like not having the clock on their screen all the time. But it takes up a little more space, and I find that not having all my menu bar icons visible makes it a little easier to focus.
Need even more space? If you have an iPad you can use it as a second monitor for your Mac, As I said hereBasically, if your iPad is nearby, you can go It shows In System Settings, click , button, and add your iPad as a display. I really like using it while on the road – it gives me a little extra space to work when I'm away from my desk and external monitor.