What is a Provisional Patent?

Actually there is no such thing as a USPTO provisional patent. 

There is however a provisional patent application that an inventor may optionally file for purposes of obtaining patent pending status on his/her invention for up to one year.

Filing a provisional application does not provide any patent rights to the inventor, and patents do not issue on US provisional patent applications.

Is there a benefit to an inventor from filing a provisional patent application?

Filing a provisional application can provide a significant benefit to an inventor, IE the provisional application provides a filing date which the inventor may claim benefit of if he/she files a nonprovisional patent application within one year of filing the provisional application.

Since US patent law operates under “first to file” principles, it is advantageous to an inventor to obtain the earliest possible filing date for his/her invention that it is possible to obtain. 

However, to obtain a patent on an invention, an inventor must file a nonprovisional patent application at some point.

A nonprovisional application may optionally claim benefit of the filing date of a US provisional  application that was filed up to one year earlier, as long as the US provisional discloses the same material as the nonprovisional patent application.

Other advantages of provisional applications to inventors are that these patent applications do not require claim sets and formal patent drawings, nor do they require Information Disclosure Statements. These reduced requirements enable an inventor to file a provisional patent application faster and earlier than a non-provisional patent application. 

Can a provisional patent search be performed?

Provisional patent applications by themselves do not issue as patents, so there is nothing to search in that regard. 

Provisional applications are not published by the USPTO and we are not aware of any way to perform a search of provisional patent applications.