This section of the Developer Tab lets you know the last step that was taken by the user before the error occurred. This can be helpful not only knowing what the person clicked but also if they also possibly typed something.
You can see that the majority last actions before the error occurred were clicked on "submit order". You can also see other reproduction steps, such as typed in certain fields. This shows you a few of the many different last steps you could potentially before your error occurred and this is useful in solving the error, since you now know the last step before it.
If you click on one of the reproduction steps here you will be taken to all of the sessions which contained this reproduction step. This can be very useful when searching for user impact on errors.