What does it mean?

[coobersdoobers]

What does this paragraph means?

node also has a mechanism for searching an array of paths, but this mechanism is deprecated and you should be using node_modules/ unless you have a very good reason not to.

How those two things are releated?

[emilbayes]

It's a reference to $NODE_PATH, but its use is highly discouraged. You can read more about NODE_PATH and how the module loading algorithm works here: https://nodejs.org/api/modules.html#modules_loading_from_the_global_folders