XDR, also known as External Data Representation, is a binary serialization data format used extensively in the Stellar Network.
The ledger, transactions, results, history, and other data on the Stellar Network are encoded using XDR.
Transactions are the basic unit of change in the Stellar Network and are essentially a grouping of operations. Transaсtions can include one or more operations.
If you have a multisig solution configured on your account, your service or wallet may provide you with Transaction Envelope XDR string.
Transaction Envelope XDR contains the transaction information together with the signature generated using the secret key of your account. If you are using multisig, you will need to add one or more additional signatures for this transaction to be accepted by the network.
This string should be provided to the owner of signing account and imported to the signing service, like LOBSTR Vault or StellarGuard.
The good news is that LOBSTR Vault saves you time and manages this process automatically - you won't need to import the Transaction XDR manually.
If you are using LOBSTR Vault paired with LOBSTR wallet, StellarTerm or Stellarport, your pending outgoing transaction will appear in the connected LOBSTR Vault account in a matter of seconds.
Connected LOBSTR Vault account will show a push notification asking to confirm or deny every new transaction.