iOS is a mobile operating system developed and distributed by Apple Inc., primarily for Apple's mobile devices. If you show proficiency in iOS, it means you have an adept understanding of its functionality, tools, design guidelines, and the capabilities of related Apple devices. This knowledge extends to both system-specific hardware and software configurations.

Advanced iOS skills might include the ability to develop apps or build frameworks for Apple devices using Objective-C or Swift, Apple's very own programming language. As an iOS expert, you could be responsible for designing and building mobile applications, scrutinizing and maintaining coding standards, debugging code, or even addressing and resolving software defects.

Understanding of Apple’s design principles and interface guidelines is indispensable, as well as the utilization of Cupertino (iOS) design across iOS apps. Familiarity with iOS core frameworks, such as UIKit, Core Data, Core Animation, etc., is of great value. Proficiency in APIs and cloud messaging, along with capabilities of handling push notifications, is also prominent.

Those who can navigate iOS's seamless interface efficiently may be well-prepared for roles such as mobile app developer, mobile UX/UI designer, or quality assurance tester in tech companies or IT teams across various sectors.

Related foundational skills useful for learning or mastering iOS include a strong understanding of computer science fundamentals, data structures, algorithms, and software design. Previous experience in other coding languages, particularly Objective-C or Swift, is pivotal. Familiarity with macOS or Unix-based systems can be beneficial. Experience with Version Control Systems like Git or similar platforms is plus.

Additional knowledge, like using Apple's Xcode development environment or working with collaborative tools like Jira or Trello, is significantly advantageous. Being aware of memory management, multi-threading concepts, or Secure Coding Practices could also be a part of this 'Tech Skill' category.

For employees and candidates, acquiring proficiency in iOS could open doors to exciting career opportunities within the tech industry. Businesses looking for tech-savvy, creative individuals with a comprehensive understanding of mobile technology will see value in those proficient in iOS.