When the Government of India (GoI) mandated Aadhar for provision of many services (subsidies, marriage certificates, death certificates, collect taxes- people without aadhar can no longer pay income tax - etc) it was challenged legally in the courts. One of the main arguments was that Indian citizens had a fundamental right to privacy, and such 'enforced' collection of biometrics violated that right.
The Attorney General (appearing for the government) argued that there was no such fundamental right, and that citizens had no right to privacy.
This (whether or not privacy is a fundamental right) had to be resolved before these cases could move forward.
So the question was 'forwarded' to a 9 judge 'constitutional bench' to rule upon. Today all 9 judges ruled that Indian citizens had a fundamental right to privacy.
so now the Aadhar specific cases can go forward, now that there is a 'constitutional bench' ruling. A 5 judge bench will now consider those cases and rule upon the legality of Aadhar enforcement.
This ruling, that privacy is a fundamental right, will obviously affect the outcome of the Aadhar specific case(s) but how exactly - including what restrictions if any, could be placed on biometric collection via aadhar - is not known (yet).
That is my non lawyerly understanding of where things stand.
This is a 'high level' ruling, which unlocks the 'deadlock' on the cases about the legality (or otherwise) of biometric collection via Aadhar for specific government schemes.
The Attorney General's argument that citizens have no fundamental right to privacy has been invalidated/overruled/whatever-the-correct-legal-term-is, by the constitutional bench. He (and his team) have to find new arguments now. [1]
The lawyers of both sides on those cases, now have to proceed on the assumption that privacy is a fundamental right. The pro-govt (so pro -aadhar) side will likely argue for 'reasonable restrictions' on the right. The anti govt side will likely argue that such restrictions are not 'reasonable' and that aadhar violates fundamental rights (or so my lawyer friends tell me [2]).
[1] Tangential: The AG who made that argument has retired, and there is a new AG who will appear for the government.
[2] They are probably oversimplifying, so I can get the gist, the same way I would if I had to explain some complex programming to them. I'm not a lawyer. :-)
"Aadhaar hearings were gridlocked, withtout this judgement. Now it's legality will be tested."
Also, I recall the Indian Government was pushing Aadhar Pay - a biometric fingerprint scan based PoS payment / verification system (likely it is already deployed, I don't live there so I don't know). What happens to that now?