This is a technology for signing transactions with several private keys to improve security and privacy. It is supported by bitcoin, ether and other popular crypto-currencies.
With the help of multi-signature, you can collectively manage one crypto-currency account, both family and corporate. Transactions are conducted with the participation of a third party, which acts as a guarantor.
You can use multi-signature yourself. To do this, configure the transaction confirmation from different devices. For example, when sending a transfer from a laptop, confirmation from the smartphone is required.