There are two ways of disposition of property broadly. Testamentary and nontestamentary. WILL is testamentary disposition. All other means are nontestamentary.
WILL is not a compulsorily registerable document. But beneficiary claiming under a WILL or a legatee or executor named in the WILL to when proceed with the WILL would advertise in the newspaper stating that such a WILL has been executed with respect to specific properties mentioned therein and any other holding claim in the said properties may approach the legatee or executor within say one month failing which the properties would be executed as per the said WILL. This is because before executing it has to be confirmed that this is the LAST WILL. If there are no other claimants the WILL along with advertisement can be taken forward for registration with the registry and mutation can be effected accordingly. If there is any other WILL dated post to the advertised one or there is a CODICIL(amendment) the same would be the valid one.
In case of any disputes the same would need to be taken to civil court.
Probate is a document issued by civil court declaring that a particular WILL is the last and final WILL and is valid to be given effect. But according to my understanding only those WILLs executed within the presidency towns need to be probated compulsorily now , others are not.
You may also refer to sec 213 of Indian succession act for further clarifications.
Correct me if I have gone wrong pls.