The Start Menu

The start menu started off as a simple toolbar of sorts, filled with shortcuts. Here's a screenshot of the start menu in Windows 95. It's a bit underwhelming, but it does the job. Notice that there's no search field: you have to click until you find the program you want to launch / the setting you want to access:

The start menu in Windows 7 wasn't too different from that screenshot, but it had a search field (introduced in Vista). Today, Windows 10 ships with two distinct start menus: one that takes up the entire screen when you're in tablet mode, and one that looks more like a desktop experience, but with tiles on the right. Here's my start menu on this laptop. I did not customize it in any way, other than Windows 10 showing recent files / recently installed programs:

The start menu is basically the content of two folders

The start menu is mostly a collection of shortcuts. These shortcuts come from the content of two folders: one folder is under your own Windows profile. Anything in that folder is only shown in your start menu. The second folder is shared between all users on that PC. Anyone using your PC will see shortcuts to core programs like Notepad or Paint, for example.

When you install an app, the installer will often ask for the administrator's password: if so, you know that the app will be installed in one of the "Program Files" folders. All users will see a shortcut to apps stored in Program Files.

FYI: there's a "C:\Program Files" folder, where 32-bit (older) programs are stored. And there's a "C:\Program Files (x86)" folder, where more modern programs are stored. It doesn't matter why for our purpose: just know that your apps are primarily stored in one of these two folders. The two program-files folders in Windows 10

Can I access these two folders?

Good thinking, boss: yes, you can access these folders. In older versions of Windows, you could drag-and-drop shortcuts onto the start menu. That's no longer the case in Windows 10 (notice the "forbidden" cursor in the screenshot). So, we'll go to these folders in File Explorer (Windows Explorer) to add custom shortcuts to our start menu - or to remove some apps.

A shortcut is a special type of file that contains a reference to a "target file". If you right-click on an icon in the start menu and choose "More > Open file location", a folder will open in File Explorer. This will be the folder that contains the shortcut, not the folder that contains the target file / program.