When your main script is run and your instance of Vue is set up, it goes through a series of initialization steps. As we said earlier, Vue will walk through your data objects and make them reactive, as well as compile the template and mount to the DOM. Later in the lifecycle, Vue will also go through updating steps, and later still, tear-down steps.
Here is a diagram of the lifecycle instance taken from http://vuejs.org. Many of these steps concern concepts that we haven't yet covered, but you should get the gist:
Figure 2.11. Vue.js lifecycle diagram
Vue allows you to execute custom logic at these different steps via lifecycle ...
