This tag should be used for MultiBit, a now defunct lightweight Bitcoin client.
Multibit is a lightweight Bitcoin wallet. It does not store the full blockchain and must ask full nodes for transactions pertaining to the wallet. Its disk usage is minimal as it only stores the block headers to ensure that it is connected to nodes using a blockchain with the most work.
Multibit was acquired by KeepKey which has since stopped development work on Multibit. It has several known issues which will likely never be solved as the software is no longer supported.
Questions related to the usage and development of Multibit should use this tag.