The seven days between Rosh Hashana and Yom Kippur are an opportunity to do Teshuvah with respect to each of the seven days of the week -- i.e., on the Monday, we can make amends for whatever wrongs we may have done on all the Mondays of the previous year... and so forth.
The Shabbat between Rosh Hashanah and Yom Kippur, is called " Shabbat Shuvah," after the Prophetic reading (Haftorah) for this day: " Return, O Israel..."
