أَسْتَغْفِرُ اللهَ رَبِّي مِنْ كُلِّ ذَنْبٍ أَذْنَبْتُهُ عَمَدًا أَوْ خَطَأً، سِرًّا أَوْ عَلَانِيَةً، وَأَتُوبُ إِلَيْهِ مِنَ الذَّنْبِ الَّذِي أَعْلَمُ وَمِنَ الذَّنْبِ الَّذِي لَا أَعْلَمُ، إِنَّكَ أَنْتَ عَلَّامُ الْغُيُوبِ وَسَتَّارُ الْعُيُوبِ وَغَفَّارُ الذُّنُوبِ، وَلَا حَوْلَ وَلَا قُوَّةَ إِلَّا بِاللهِ الْعَلِيِّ الْعَظِيمِ
Transliteration
Astaghfirullaaha rabbee min kulli dhanbin adhnabtuhu amadan aw khata-an, sirran aw alaaniyah, wa atoobu ilaihi minadh-dhanbilladhee a'lamu wa minadh-dhanbilladhee laa a'lamu, innaka anta allaamul ghuyoobi wa sattaarul uyoobi wa ghaffaarudh-dhunoob, wa laa hawla wa laa quwwata illaa billaahil aliy-yil azeem.
Translation
I seek forgiveness from Allah, my Lord, from every sin I committed knowingly or unknowingly, secretly or openly. I turn to Him from the sin I know and from the sin I do not know. Surely You are the Knower of the unseen, the Concealer of faults and the Forgiver of sins. There is no power and no strength except with Allah, the Most High, the Great.
Simple meaning: This Kalima teaches asking for forgiveness for known and unknown mistakes.