This is a conceptual and rather basic question. So I know HTML, CSS, JS and now AngularJS.
And I was wondering how I could build functional web apps without knowledge of server side programming languages - and chanced upon Firebase.
Could someone please explain to me how I could use Firebase to build web apps - with my limited knowledge in mind?
Building a full-featured web application without any server-side logic and input validation does not make much sense.
If you are unwilling to learn a server-side language and a proper framework, take a look at NodeJS. It allows you to write server-side code in JavaScript, so if you catch up on security principles you should do OK.
Good luck!