Angular Ivy is the new rendering architecture that comes, by default, with version Angular 9. The Angular rendering architecture is not new to a complete revamp, Angular 2.0, Angular 4.0 and now Angular 9.0 have introduced new compilers and runtime engines.
Currently, Angular stable version is 9
The post contains the thoughts of a preliminary investigation on how Angular works reading some parts of the source code, debugging a simple application and reading how the compiler works. Some terms or definition could be wrong.
This post is quite useful if you want to get a deep understanding of Angular Ivy which is now the default rendering engine in Angular 9