Money allows you to transfer funds between accounts, creating transactions in two different accounts that Money knows are related. When a transfer is created from an account, a corresponding entry is automatically created in the selected destination account. Likewise, changes to a transfer transaction in one account are automatically applied to the corresponding entry in the other account.
When the selected transfer origin and destination accounts have different currencies, Money performs the exchange automatically, using the latest rate in the Money > Preferences > Currency exchange rate table. The used rate will appear in the transfer transaction of the destination account, and you will be able to edit it manually.