I have been seeing this sort of thing around a lot while customizing themes.
<?php esc_attr_e( 'Skip to primary content', 'twentyeleven' ); ?>
Why does it say "twentyeleven" in there? I am seeing this in a ton of different PHP functions in multiple themes (different name depending on the theme of course).
I tried removing them to see what it would do, and it didn't break anything. So what purpose do they serve?