Answer:   This is a new concept for the people who are not familiar with Syntax. Angular Directive is a function and it will fire whenever Angular Compiler identifies the directive in the DOM. The imported Directive symbol provides the Angular @Directive decorator. Basically Angular Directives are used to extend the power of HTML by giving it a new Syntax and there are three types of Directives in Angular:
1. Components : Directives with a template.
2. Structural Directives : Change the DOM layout by adding and removing the DOM elements.
3.Atribute Directive : Change the appearances and behavior of elements, components or another directive.