Angular is a framework which allows people to create responsive single page web apps. It is built on TypeScript and can be used to build scalable web apps, has a collection of well-integrated libraries which cover many features and several tools to help build, test and maintain your code. With Angular you can create single-page-application where you have a single html file where changes are rendered in the browser. Familiarity with HTML/CSS as well as JavaScript/TypeScript will be needed while building your web app.
Official Angular documentation can be found here.
https://angular.io/docs
Sololearn offers a free Angular course.
https://www.sololearn.com/learning/1092
udemy also offers a deeper and more comprehensive Angular course although you do have to pay for it.
https://www.udemy.com/course/the-complete-guide-to-angular-2/
stackblitz is a great way to test your code online for free with your github account.
https://stackblitz.com/
Angular also has its own set of official sources which can be found here.
https://angular.io/resources?category=community