Some of the advantages of filing a provisional patent application rather than a complete or non-provisional application are lower cost and faster time to file.
A provisional might be 10 to 25% of the cost of a non-provisional. A provisional might be filed in a couple of days, whereas a non-provisional might be filed in about 30 or more days.
A faster time to file means an earlier filing date. An earlier filing date means an increased probability of being the first to file a patent application on the invention. Being the first to file means you get the patent instead of a later filed application.
But as with most things, with advantages come disadvantages and traps.
In a rush to file a provisional application, important details of the invention might be unintentionally omitted from the application. Details might be omitted because they did not even exist at the time of filing.
However, the omission of important details might be the difference between being the first to file and the second to file.
Here is an example.
On day 1, inventor Abe files a provisional patent application that includes the inventive features of A and B.
On day 2, inventor Bob files a non-provisional patent application that includes the inventive features of A, B and C.
On day 3, inventor Abe files a non-provisional application that claims "priority" to his provisional application. Abe's non-provisional application includes the inventive features of A, B and C.
Inventor Bob gets the patent for features A, B and C because he was the first to file.
So when filing a provisional application, it is important include as much detail as possible - given the time and budget constraints.