What does it mean to lazily install a dependency

On the following page, it says;

With Ember 2.11 we are now using the ember-source module and no longer the ember Bower package. In the upcoming Ember CLI 2.12 release, Bower will also no longer be installed by default and only install lazily when an addon requests it.

I wanted to understand what does the following mean "only install lazily when an addon requests it" ?