Many programs that you install are automatically run when you start your computer and load Windows. Malware has been known to use this method to load itself when a user logs on to their computer. This method allows the malware program to load in such a way that it is not easy to stop. Windows does offer a program that will list programs that are automatically started from some of these locations. This program, Msconfig.exe, only lists programs from a limited amount of startup keys, but I will note when it is otherwise.
Source: https://www.bleepingcomputer.com/tutorials/windows-program-automatic-startup-locations/