In the Stellar network, transactions are encoded using a standardized protocol called External Data Representation (XDR).
When you post a transaction, a client will encode the transaction as XDR before submitting it to Horizon.
When you request a transaction, Horizon returns some data about the transaction in human-readable JSON. The full canonical data about the transaction is encoded in machine-readable XDR, available in XDR attributes at the end of the response.
You can decode this XDR in the Stellar Laboratory’s XDR Viewer.
The XDR encoded transaction as stellar-core sees it.
The effects of a transaction encoded in XDR.
The details about the effects of a transaction encoded in XDR.
The fees associated with the transaction encoded in XDR.