Apple released iOS 10.3.2 for compatible iPhone and iPads on May 15, and today, it has stopped signing iOS 10.3.1. This means that users will not be able to downgrade to iOS 10.3.1 from iOS 10.3.2 if they had not already saved the SHSH blobs.
Like iOS 10.3.1, iOS 10.3.2 is a minor update aimed at fixing some bugs and patching some security exploits.
Usually, iPhone or iPad owners downgrade to an older version of iOS since they are easier to jailbreak. However, the last stable and working jailbreak for iOS released to the public was for iOS 10.2 by the Yalu jailbreak team.
Apple has also been beta testing iOS 10.3.3 which is again a minor release aimed at fixing bugs and improving the security of the OS. It is likely going to be the last release of the OS before Apple releases iOS 11 later this year.