What is NX ?
Nx(Narwhal extension) is not a replacement of angular CLI, it is just an extension for the Angular CLI implementing monorepo-style development. It is an open-source toolkit created by Ex Googlers at a company called Narwhal for enterprise applications. It is also a collection of runtime libraries, linters, and code generators, which is helping large teams build better with Angular.

NX Workspace
A NXworkspace contains our Angular applications and libraries we create. Nx is not a replacement of Angular CLI, it just adds some extra capabilities to Angular CLI, so finally we can say an Nx workspace is an Angular CLI workspace.

Creating a New Nx Workspace
npx create-nx-workspace@latest workspacename --preset=angular //Using npx
npm init nx-workspace workspacename --preset=angular //Using npm init
yarn create nx-workspace workspacename --preset=angular // For Yarn

Conclusion
Like NX workspace, with Angular CLI also we can add different types of projects to a single workspace. This is great, but it is not sufficient to enable the monorepo-style development. Nx adds an extra layer of tooling to make this possible. Click here to learn full version of NX Tutorials