Signing is the process of associating your identity with information so that it could be verified that the information is coming from you.
In the physical world, we sign documents by putting our initials or signature in ink at the end of the text. When we have to fill a form or submit a document in a public office, this is generally the process for signing.

Cryptographic Signing
In the digital world, we sign the data cryptographically. The process of cryptographic signing involves hashing the data and then encrypting that hash with the user’s own private key. The ciphertext of the hash is the signature of the data and it is appended to the data (just like we sign the physical documents at the end).
The signature could be then verified by the receiving party by decrypting the signature using the sender’s public key. The receiver would then hash the data at their end. These two hash values — decrypted signature and hash of the data — must match for the signature to be valid.

Signing in Blockchain
In the context of blockchains, signing is used for verification of transactions and blocks. The users sending transactions must sign them before submitting them to the nodes; also the miners or validators must sign the blocks before proposing them to the chain. The authenticity of the data in a blockchain is verified using cryptographic signing.

Signing is not Encryption
There is a small misconception that all data on a blockchain is encrypted. This is not correct. All the data on a blockchain is signed and signing is not encryption. Signing is used for associating identity with the data while encryption is used for hiding the data. Both have clearly different use-cases.

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