The Angular applications are written in TypeScript and HTML. Their components and templates must be converted to executable JavaScript by the Angular compiler. There are two types of compilations in Angular:
Just-in-time (JIT) compilation: This is a standard development approach which compiles our Typescript and html files in the browser at runtime, as the application loads. It is great but has disadvantages. Views take longer to render because of the in-browser compilation step. App size increases as it contains angular compiler and other library code that won’t actually need.
Ahead-of-time (AOT) compilation: With AOT, the compiler runs at the build time and the browser downloads only the pre compiled version of the application. The browser loads executable code so it can render the application immediately, without waiting to compile the app first. This compilation is better than JIT because of fast rendering, smaller application size, security and detect template errors earlier.