Improve npm documentation for dependency management (#7146)

* Added a more descriptive explanation as to what npm does, and what dependencies are.

* Added a more descriptive explanation as to what npm does, and what dependencies are, including punctuation.

* Update apps/site/pages/en/learn/getting-started/an-introduction-to-the-npm-package-manager.md

Signed-off-by: Brian Muenzenmeyer <[email protected]>

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Signed-off-by: Brian Muenzenmeyer <[email protected]>
Co-authored-by: Brian Muenzenmeyer <[email protected]>

Author: Makena-Wambui

apps/site/pages/en/learn/getting-started/an-introduction-to-the-npm-package-manager.md

@@ -18,7 +18,7 @@ It started as a way to download and manage dependencies of Node.js packages, but
 
 ## Packages
 
-`npm` manages downloads of dependencies of your project.
+`npm` installs, updates and manages downloads of dependencies of your project. Dependencies are pre-built pieces of code, such as libraries and packages, that your Node.js application needs to work.
 
 ### Installing all dependencies