Packages specified in packages.json/bower.json and build output

Does all of the source code for packages specified in packages.json OR bower.json not end up as being part of the build output (i.e. under dist directory (vendor.js, appName.js, etc)) ?

If no, what ultimately ends up in the build output (apart from that under /app folder which gooes to appName.js) ? Does that depend on ember-cli-build.js ?

Also if any package code does not form part of the build output, does it mean that it is redundant OR it can be just dev dependency or some other use case (pls provide example of any other case)