Browser Runtime ↔ JS Runtime Environ with JS Engine, Web API, Callback Queue & Event Loop
Callback Queue
Data structure "todo" list of Callback Function to await execution

References
Front-End App (JS)↔ App to Execute in Browser Runtime with access towindow(Global Object)Web API↔ API Collection extends Browser Runtime (viawindow)JS Global Function↔ built-in function to access in Global Scope of Browser RuntimeWeb Platform↔ Collection of Open Standard Technologies incl HTML, CSS, ECMAScript & Web Assembly, mainly for Browser Runtime