A codec is the logic to encoding or decoding a media stream, there are many different types with popular ones being H.264, HEVC (H.265) and MPEG-4.

Codecs are different to containers like MP4, MKV and MOV because a codec manages the bitrate, resolution and frames whilst the container organizes and returns the data as sequence. Think putting many frames and audio together and playing them back or when you skip ahead providing the right data.

Codecs

To list all codecs in FFmpeg simply do

ffmpeg -codecs

The guide for the returned codecs is:

D..... = Decoding supported
.E.... = Encoding supported
..V... = Video codec
..A... = Audio codec
..S... = Subtitle codec
...I.. = Intra frame-only codec
....L. = Lossy compression
.....S = Lossless compression

DEV.LS h264    H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (decoders: h264 h264_qsv h264_cuvid ) (encoders: libx264 libx264rgb h264_amf h264_nvenc h264_qsv nvenc nvenc_h264 )
DEV.L. hevc    H.265 / HEVC (High Efficiency Video Coding) (decoders: hevc hevc_qsv hevc_cuvid ) (encoders: libx265 nvenc_hevc hevc_amf hevc_nvenc hevc_qsv )

Looking at two popular codecs returned, h264 has DEV.LS whilst h265 has DEV.L meaning h265 is missing Lossless compression ability (In this version).

You can also see the encoders and decoders for each codec.

Encoders

List all encoders with:

ffmpeg -encoders

This again has a key

V..... = Video
A..... = Audio
S..... = Subtitle
.F.... = Frame-level multithreading
..S... = Slice-level multithreading
...X.. = Codec is experimental
....B. = Supports draw_horiz_band
.....D = Supports direct rendering method 1

V..... libx264   libx264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (codec h264)

libx264 encoder only supports video (V) also provided  is the codec.

To view more details on an encoder

ffmpeg -h encoder=libx264

This will return all options and parameters when encoding with this encode method.

Decoders

The same can be done with decoders, to list all of the decoders:

ffmpeg -decoders

View more details:

ffmpeg -h decoder=aac

Containers

List all containers (formats) with FFmpeg:

ffmpeg -formats