Displaying texts in template files

I hope the topic name is relevant. Dunno what to name this

In some themes I have seen this tag:
_e(‘What is this, the whole tag’)

and in Sandbox template I found this
link_pages(“\t\t\t\t\t<div class=’page-link’>”.__(‘Pages: ‘, ‘sandbox’), “</div>\n”, ‘number’);

From what I see they are just text, nothing more. But why a tag or two just for this?
Why does the sandbox one has a ‘sandbox’ after the text?