Ishraq prayer is voluntary while Thuhur prayer is a fard and it is mandatory.
Ishraq prayer is one of the formats of praying Duha prayer.
It is to be prayed after praying Fajr in the masjid and waiting until the sunrises while making thikr or reading the Quran.
After about 15 minutes of sunrise, one prays two rak’ah and this is Ishraq prayer.
It is equivalent in reward to performing Hajj and Umrah.