The Windows 10 taskbar is a often-used place because it will list all of your applications that are currently active/opened, as well as any applications that you have pinned to it. It also contains the start button, the time, …
But it can get busy over there, especially if you have many applications that are opened/active. And you can get lost in all those windows, especially if you have multiple active windows from the same application.
The default behaviour in Windows 10 is to group those applications into one button. This way, the icon is shown once, but with a visual that indicates there are more than 1 windows for that same application.

Disable taskbar grouping in Windows 10 by first right-clicking on the taskbar. Then go to Taskbar Settings. There, you will see the option ‘Combine taskbar buttons’. Simply disable this toggle.
You will now see that for each of your applications that are open, the taskbar buttons are no longer combined but separate.