Indian Patent Law follows first to file system. Provisional specification describes the nature of the invention to have the priority date of filing of the application in which the inventive idea has been disclosed.
It must be followed by a complete specification describing the details of the invention along with a statement of claims within 12 months after filing of the provisional application. If the complete specification is not filed within the prescribed period, the application is treated as deemed to have been abandoned.
Generally, an application filed with provisional specification is known as provisional application which is useful in establishing a priority date for your invention. Moreover, filing of a provisional application is useful as it gives sufficient time to the applicant to assess and evaluate the market potential of his invention before filing complete specification. However, it is not necessary to file an application with provisional specification and one can file application directly with complete specification.