Stayman and Blackwood are common examples of relay bids.
Instead, only one partner can make the cheapest bids available (relays) while the other describes his hand.
While relay systems offer a higher level of exchanged information than natural systems, they also have the drawbacks that they are complicated to memorize and often exclude the players' judgment, particular in regard to honor location, which can be crucial.
The descriptive response can be natural (as in Stayman) or coded (as in Blackwood).
Thus technically it's a relay but with the cheapest bid expected most of the time.