Any NGO, a Section 8 corporation or charitable trust can apply for registration under Section 12 A if it wants to get an exemption from income tax. Without the 12a certificate for NGO, the receipts of the NGO will be entitled to normal tax rates.
To summarise, registering under the 12A section allows the NGO exemption from tax rates. Failing to do will make them applicable for ITR filling. The 80G section, on the other hand, ensures that a person donating to the NGO can deduct the amount from their taxable income, which leads to more donations.
By 12A registration trusts and NGO enjoy exemption from paying taxes. 80G registration provides benefit to the donor of an NGO.