The 10-day period beginning on Rosh Hashahnah and ending on Yom Kippur is known as the "Ten Days of Repentance"; this is the period, say the sages, of which the prophet speaks when he proclaims (Isaiah 55:6) "Seek G-d when He is to be found; call on Him when He is near." Psalm 130, Avinu Malkeinu and other special inserts and additions are included in our daily prayers during these days.
The Baal Shem Tov
instituted the custom of reciting three additional chapters of
Psalms each day, from the 1st of Elul until Yom Kippur (on
Yom Kippur the remaining 36 chapters are recited, thereby completing the entire
book of Psalms). Click below for today's three Psalms.