We already get a lot of value from Helm by being able to take a single value from a chart and include it in a number of places throughout a chart, like the example earlier in the chapter, where we referred to the same port number in several related places. You might also use this technique, for example, to ensure a system with a number of different components provided by different containers are always deployed to the same version number.
Another important way that we can use variables in our Helm charts is to provide a signal to our template to change our configuration or even turn whole features into optional extras that might not always be enabled.
There are three constructs that allow us to construct really powerful abstractions ...
