Ijaza or Ijazat is a certificate, license, permission, and authorization that grants its holder the right and authority to transmit and teach Qur’an, and it is issued by someone who has and possesses the authority of transmitting Qur’an. Moreover, it gives its holder the eligibility to certify others with the same authority.
You have to know that Ijazah has two types:
By obtaining Ijazh and transmitting it to others, this process makes like an endless chain of certified Qur’an narrators.
Prophet Muhammad (PBUH) said “The best among you are those who learn the Qur’an and teach it”