Martin Brinkman gives a full explanation of what it is and how to remove it on his website
here.
Here's a copy/paste for archive purposes, the website itself might be easier on your eyes.
How to remove the Meet Now icon on Windows 10
Meet Now is useful to a subset of users. If you don't plan to use it, you may want to remove it from the taskbar as it takes up space without providing anything of use to you.
Multiple options are available to remove Meet Now from the system. One of the easier options involves right-clicking on the Meet Now icon and selecting "hide" from the context menu that opens. Doing so removes the Meet Now icon from the Windows 10 taskbar.
Another option that you have is to open the Settings application on the system, e.g. by using the shortcut Windows-I, or by selecting Start > Settings, going to Personalization > Taskbar, selecting "turn system icons on or off", and toggling "Meet Now" on the page that opens to off. You may restore Meet Now at anytime using the Settings app, but need to make sure the feature is set to on this time.
Removing Meet Now via the Group Policy
System administrators may disable (or enable) the Meet Now icon on the Windows 10 taskbar using the Group Policy. The Group Policy is only available in professional editions of Windows 10, and not in Windows 10 Home.
Here is how that is done:
You need elevated rights to use the Group Policy.
Use Windows-R to open the runbox.
Type gpedit.msc and select OK.
Go to User Configuration > Administrative Templates > Start Menu and Taskbar
Double-click on "Remove the Meet Now icon".
Set the feature to "Enabled" to hide the icon on the taskbar of the Windows 10 operating system.
Restart the PC.
Removing Meet Now using the Registry
You may also remove Meet Now on Windows 10 using the Registry.
Use Windows-R to open the runbox.
Type regedit.exe and select OK.
For individual users, go to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
Right-click on Explorer and select New > Dword (32-bit) Value.
Name it HideSCAMeetNow.
Set its value to 1.
For all users, go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer
Right-click on Explorer and select New > Dword (32-bit) Value.
Name it HideSCAMeetNow.
Set its value to 1.
Restart the PC.