Rosh Hashanah is a time of judgement, self-reflection, and renewal. So if I have offended, upset, or caused you any harm - please can I ask for your forgiveness? Also, I forgive any offense, upset, or harm that you may have caused me.
At Rosh Hashaah we add some piyuttim (singula piyut) liturgical poems to our prayers. Here is a vidoe of Victoria Hanna explaining the pronunciation and provides insight in to its meaning.