HTML. First developed by Tim Berners-Lee in 1990, HTML is short for HyperText Markup Language. HTML is used to create electronic documents (called pages) that are displayed on the World Wide Web. Each page contains a series of connections to other pages called hyperlinks.
Formal methods. In computer science, specifically software engineering and hardware engineering, formal methods are a particular kind of mathematically based techniques for the specification, development and verification of software and hardware systems.
A high-level description is one that is more abstracted, describes overall goals and systemic features, and is typically more concerned with the system as a whole, or larger components of it. In formal methods, a high-level formal specification can be related to a low-level executable implementation (e.g., formally by mathematical proof using formal verification techniques).