A provisional application provides the means to establish an early effective filing date in a later-filed nonprovisional application.
It will not "become" a patent. The applicant must either follow up with a nonprovisional application within 12 months of filing, or petition to convert it to a nonprovisional application. A provisional application expires 12 months from the filing date. This cannot be extended; therefore, the corresponding nonprovisional application must be filed within that 12 month period to receive the benefit of the provisional.
See Provisional Application for Patent for more info.