Basically, a hash value is meant by hash (Eng. chop up, scatter). A hash value combines a lot of information that is assigned via a hash function, whereby the hash function can transfer a character sequence of any length. The same data always leads to the same hash, but if only a single bit of the data is changed, the hash looks completely different.
In the blockchain, a hash is a uniquely created character string that encrypts the data of a transaction and thus maintains its security.