First make sure you have installed node.js 8.X and npm 6.X version. You can check it on your own terminal window simply by entering node -v and npm -v. You can also download latest nodeJs from here.
$ npm -v$ node -v
Ionic 3 framework targets IOS, Android and Window platforms. So you need to install their respective SDK to make a build. Even if you don't have SDK configured, still you can run this app in own browser.