esc_html_x function is very similar to the
esc_html__ one, but has the addition of a comment section where context for the translator can be supplied. This is sometimes beneficial to use as the English language has words and phrases which can have different meanings dependent on context.
For example, the word minute:
$str = esc_html_x('Minute', 'measure of time', 'plugin-text-domain');
$str = esc_html_x('Minute', 'extremely small', 'plugin-text-domain');