In the “extras” field, the errors returned are referred to as “Result Codes” and are Horizon’s abstraction of “Stellar Protocol Codes”, which are more specific codes available in the XDR. Result Codes are Horizon’s way of normalizing Stellar Protocol Codes.

There are three types of Result Codes:

Result Code Types
Transaction Result Codes	Generic errors about transaction failures.
Operation Result Codes	Generic errors about operation failures.
Operation-Specific Result Codes	Errors specific to each operation type.