What is the difference between seeking forgiveness (Istighfar) and repentance (Tawbah)?

Istighfar (seeking forgiveness) is saying "Astaghfirullah" (I seek forgiveness from Allah) to ask for forgiveness, and repentance (tawbah) is returning to Allah the Almighty. Istighfar is one of the greatest forms of remembrance (dhikr), and the Prophet, peace and blessings be upon him, used to repeat it frequently in a single sitting, saying one hundred times: "O Allah, forgive me and accept my repentance, for indeed You are the Acceptor of Repentance, the Most Merciful." Istighfar becomes repentance if it fulfills the conditions of repentance: abandoning the sin, resolving not to return to it, and regretting what has passed. Thus, istighfar and tawbah overlap.