وَإِنِّي لَغَفَّارٌ لِّمَن تَابَ وَامَنَ وَعَمِلَ صَالِحًا
...
And verily, I am indeed forgiving to him who repents, believes and does righteous good deeds,
meaning, "Whoever turns to Me in repentance, then I will accept his repentance regardless of whatever sin he did."
Allah, the Exalted, even accepts the repentance of the Children of Israel who worshipped the calf.
Concerning Allah's statement,
...
تَابَ
...
who repents,
This means to turn away from what one was involved in of disbelief, associating partners with Allah, disobedience of Allah or hypocrisy.
Concerning Allah's statement,
وَامَنَ
(and believes),
This means the person's belief in his heart.
وَعَمِلَ صَالِحًا
(and does righteous deeds),
his action with his bodily limbs.
Concerning Allah's statement,
...
ثُمَّ اهْتَدَى
and then Ihtada.
Ali bin Abi Talhah related that Ibn Abbas said,
"This means that he then does not doubt."
Qatadah said,
"This means he adheres to Islam until he dies."
We see here that there is a specific order in which these things are presented.
This is similar to Allah's saying,
ثُمَّ كَانَ مِنَ الَّذِينَ ءَامَنُواْ وَتَوَاصَوْاْ بِالصَّبْرِ وَتَوَاصَوْاْ بِالْمَرْحَمَةِ
Then he became one of those who believed and recommended one another to perseverance and patience and recommended one another to pity and compassion. (90:17)