Major release version of Angular are:
The version 2.x and higher is called 'Angular' and the version 1.x or less is called 'Angular JS'
Animation Package package out from @angular/core and put into separate package. That mean if you don’t want to use that module , this extra code will not end up in your production bundles.
provide support of latest version of typesctipy i.e TypeScript 2.1 & 2.2 compatibility added.
make angular bundle Smaller & Faster as compared to previous one
ModuleID Removed which we are using for providing relative path during template URL and StyleUrls.
<Template> is now <ng-template>
Improved *ngIf with else condition.
Introduced some new Pipes like titlecase.
Angular 5:(Code is named pentagonal-donut )
Focus was on making Angular smaller, faster, and easier to use. Major changes are:
Build Optimizer- production builds created with the CLI will now apply the build optimizer by default
Angular Universal State Transfer API and DOM Support - easily share application state between the server side and client side versions of your application
Compiler Improvements - Improved the Angular compiler to support incremental compilation
TypeScript Transforms - the Angular compiler now operates as a TypeScript transform, making incremental rebuilds dramatically faster.
Preserve Whitespace - Historically tabs, newlines, and spaces in your templates have been faithfully recreated and included in your build by the compiler. You can now choose whether or not to preserve whitespace coming from your components and your application
Improved Decorator Support
Why there is no Angular 3
Angular is being developed in a MonoRepo (https://github.com/angular/angular) it means a single repo for everything. @angular/core , @angular/compiler , @angular/router etc are in the same repo and may have there own versions. Due to misalignment of the router package’s version, the team decided to go straight forAngular v4.