You have already seen a number of user-mode processes on your computer (all the applications you see are running in user mode), modifying files, connecting to the internet, and performing lots of activities. However, you might be surprised to know that user-mode applications don't actually have privileges to do all of this. In fact, they don't have the privileges to do anything except modify their own memory (without allocating or changing permissions).
For any process to create a file or connect to a domain, it needs to send a request to the kernel mode in order to perform that action. This request is done through what is known as a system call, and this system call switches to kernel mode to perform this action (that is, if the permission is granted). Kernel mode and user mode are not only supported by the OS (or software restrictions)—they are also supported by the processors through protection rings (or hardware restrictions).
