Based on the Nature, the certificates can be classified mainly in to two.
1. Educational Certificate
2. Non Educational Certificate

Also based on the rules implemented in the Country the attestation procedures can be classified in to two:
1. Certificate Attestation
2. Certificate Apostille

In India now a days the rule is following  for the Attestation procedures. It may Include:

1 .Notary certificate attestation
2. Home department certificate attestation
3. Ministry of External Affairs certificate attestation
4. Respective Embassy / Consulate certificate attestation

After all there is one more certificate attestation is there called Ministry of Foreign Affairs . This certificate attestation is done at the destination country. Normally from the destination country, the employer will ask for MFA (Ministry of External Affairs).

But infact , before geting the MFA the certifiate should be attested from the issuing country. The above four certificate attestation procedures should be completed. Then only the Certificate will be accepted for the process of certificate attestation . At Ministry of Foreign Affairs.