TinyUmbrella is a famous tool to save SHSH blobs. Although you can do the same thing with other tools like the Cydia itself or iSHSHit can also email it to you after saving SHSH hashes.
Yes we do not neglect the beginners. If you are totally unaware of this, you can check out the following paragraph to know what are these blobs and why saving them is important.
What are SHSH Blobs?
For the people who are not familiar, SHSH Blob is a signature verification file against Apple Server. It verifies that the iDevice is running the latest version of iOS. Saving SHSH blobs will allow you to restore to previous version. While doing so Apple will stop you doing the restore process. To make this happen you have send a request to different servers which forwards SHSH blobs to iTunes by just showing it that its a new version of iOS. This is how TinyUmbrella or iSHSHIT works to help you save SHSH blobs.
Too technical ?? Simply, it allows you to come back to the older firmware even if Apple stops signing it because they have introduced a new iOS version.
Download TinyUmbrella v4.33.00