Codec and encoder are blurred together constantly, and the distinction matters. A codec, short for coder-decoder, is the standard - H.264, HEVC, AV1 - that defines what a compressed bitstream is allowed to look like and how a decoder must read it. An encoder is a specific program that produces such a bitstream: x264 produces H.264, x265 produces HEVC, SVT-AV1 produces AV1, and fixed-function hardware blocks (NVENC, Quick Sync, AMF) produce any of them. The codec fixes the efficiency ceiling, since no encoder can beat its own codec's limits, but two encoders for the same codec can land far apart because reaching the ceiling means searching an enormous space of coding choices, and how much of it an encoder explores depends on the time it is given. The catch this resolves: the same AV1 codec can span roughly 18 BD-rate points from a fast hardware block to a slow software preset, so saying we use AV1 tells you almost nothing about the bitrate until you name the encoder and preset.
