Question: I have a little question about angular-cli.

Is it true that when I run **ng serve** I use the **global** installed angular-cli and when I run **npm start** the **local** one?

Answer: 
Yes it is true. 

Let's say your global Angular CLI version is 2 and you just cloned and installed a project from github that is created with Angular CLI version 1. If you run `ng serve` it will execute using version 2 (which is your global cli), if you run `npm run start` it will use the script in node\_modules/.bin folder (which is local to your project and which is the right one for the job).
Yes. It is true. **ng serve** runs the app on angular global cli on the **current version** of the installed angular version while **npm run start** runs it on the version of that **particular angular application** cloned version from the node-module.