Encoding data transforms it into another format so that it can be read by another party that has the system (algorithm, cipher) used to encode it.
Data that is encoded is made widely available by the sender, deliberately so, so that it is easily consumed by the recipient(s). The ease of access ensures that the message is delivered and although no key is needed (as in encryption), the recipient does need to have the algorithm that makes and unmakes the transformation between formats.
Once the encoded message is run through the algorithm or cipher and is in its original format, it is said to be decoded.
“The 2002 American film ‘Windtalkers’ starring Nicolas Cage and directed by John Woo depicts a true story of US Marines in the Solomon Islands. The USMC detail is charged with protected Navajo code talkers, or Native American marines who encoded sensitive messages simply by translating them into Navajo, a language with which the Axis adversaries were unfamiliar.”