email – In Gmail, how does one change the appearance of action labels at the top?

In Gmail, I have features at the top of the screen displayed as such (these icons show up when you check an email):

Someone I give computer classes to has the following labels, spelled out:

I find the second one cluttered, but the first one might be too confusing.

Are there ways to go back and forth between these two styles? Or other options for the display of labels?