Execution context and activation object in details

There are many interesting articles both in Russian and English.
You can start with this one — http://dmitrysoshnikov.com/ecmascript/javascript-the-core/#execution-context-stack. In Russian — http://dmitrysoshnikov.com/ecmascript/ru-javascript-the-core/#stek-kontekstov-ispolneniya

The short summary

Javascript runtime is synchronous and processes Execution Context Stack. It’s bottom Execution Context is global object as everything starts with this.
When some function or eval is being called, runtime places it’s Execution on context on top of the stack.

Each Execution context consists of Variable Object, Scope chain and this value.

Variable Object is a global object for global execution context. It consists of function declarations and variables which are declared in global context.

For functions Variable Object is called Activation Object and consists of function declarations and variables declared inside a function, and it also contains all function arguments and arguments map, like this: