Editing & Post-Production
Codec
Also called: encoder, compression format
The name is a contraction of coder and decoder. A codec decides how much data a picture costs and how hard a device has to work to play it back, and it is a separate thing from the container, so an MP4 file can hold H.264, H.265 or AV1 inside it.
Two families matter in practice. Delivery codecs such as H.264, H.265 and AV1 squeeze hard and are painful to edit, since every frame depends on its neighbours. Intermediate codecs such as ProRes and DNxHR are far larger and cut smoothly because each frame stands alone. Editing straight from a delivery codec is why timelines stutter on capable machines.