What is the difference between Tawbah (repentance) and Istighfar (seeking forgiveness), when should one seek forgiveness, and when should one repent, and is Istighfar for minor sins while Tawbah is for major sins?

Repentance (Tawbah) is turning away from sin, regretting it, and committing to obedience. As for seeking forgiveness (Istighfar), it is asking for pardon, for one's sin to be concealed, and not to be held accountable for it. They are interconnected, as indicated by texts from the Quran and Sunnah, such as the Almighty's saying: ﴿And [commanding you], "Seek forgiveness of your Lord and then repent to Him"﴾ [Hud: 3], and the Prophet, peace and blessings be upon him, said: "By Allah, I seek Allah's forgiveness and repent to Him more than seventy times a day." One must hasten to both at all times and in all circumstances, for all sins. Whoever constantly seeks forgiveness, Allah will make for him a way out of every worry and a relief from every hardship, and provide for him from where he does not expect.