Sometimes you have a string combined with some html or data which don't have to get into translation.
// template
{{e({ opentag: '<b>' , closetag: '</b>'}) "my template is #opentag nice #closetag"}}
// translation string:
my template is nice
// html output
my template is <b> nice </b>
Sometimes you have a string combined with some html or data which don't have to get into translation.