Q:

Explain the options for npm list [[@/] ...]

Please explain the options for the scope mentioned in the following command using a couple of EXAMPLES:
npm list [[@<scope>/]<pkg> ...]

The docs for this command does not provide a direct explanation.

A:

It's described here well enough :
Scoped Packages.
Scopes basically help in grouping similar npm packages together. Each scope will have a directory with the scope's name under node_modules and packages that come under the scope inside it.
In your example, if a scope is given it lists the packages under that particular scope, i.e. under node_modules/<@scope>/.

