Multihash is hash format that is not specific to a single hashing algorithm.
A multihash describes the algorithm used for the hash as well as the hash value.
+-----------+----------------------------+
| Hash Type | Hash Value |
+-----------+----------------------------+
SHA-256 example.
+---------+------------------------------------------------------------------+
| SHA-256 | 2413fb3709b05939f04cf2e92f7d0897fc2596f9ad0b8a9ea855c7bfebaae892 |
+---------+------------------------------------------------------------------+
Note: these examples are simplifications of the concepts. For a complete description visit the project and its specs.