The primary purpose of an Operating System is to allow users and/or services to communicate with each other. Modern OS provide these key features; Internet Connectivity, Security, Customizability. Internet Connectivity is important due to the fact that most communications happen over the open internet. Security is important for users to know that their device isn't at risk of a virus. Customizability is important because it allows users to decorate their system however they like.

The primary purpose of an Operating System (OS) is indeed to manage the computer's resources and provide an environment where users and/or services can interact with the computer hardware. This is achieved through a set of specialized software that controls and organizes tasks and functions.

The key features you mentioned are indeed important aspects of modern operating systems:

1. Internet Connectivity: This feature allows the OS to connect to the internet, enabling users to browse the web, download files, and use internet-dependent applications. It also facilitates updates and patches to the OS itself.

2. Security: This is a critical feature of an OS. It protects the user's data from unauthorized access and safeguards the system against malicious software like viruses and malware. Security measures can include user authentication, file permissions, and encryption, among others.

3. Customizability: This feature allows users to personalize their OS according to their preferences. This can include changing the desktop background, adjusting the layout of icons, and installing custom themes. It can also extend to more technical customizations like changing system settings and installing new software.

In addition to these, modern operating systems also provide other features like multitasking, memory management, device management, and system performance monitoring.