That is a very broad topic.
Many developers are calling themselves full-stack developers because this is what recruiters want..
The truth is, it can take years to truly master each domain, client, server, DB, security, performance, building tools and the list just started.. Don't forget that eventually experienced plays a major role, it takes time.
Start small, if you go with js stack, play with React, Node, and MongoDb, you can then add build tools like webpack, start optimizing, deploying and extending your knowledge
Just search for full stack development on youtube, you will find endless resources.
To understand what it means to be a full-stack web developer check this out: