Plug-ins and Web Browsers
The first Internet browsers had support for text only, and even the text support was limited to a single font in a single color. Then came browsers with support for colors, fonts and text styles, and the support for pictures was added.
The support for sounds, animations and videos is handled in different ways by different browsers. Some elements can be handled inline, and some requires an extra helper program (a plug-in).
Audio codecs can usually contain one audio channel (mono), two audio channels (stereo), or more channels (e.g. "5.1" surround). For example, human voice is recorded using one channel while music uses in general two or more channels. The quality will vary depending on the bitrate, ie the number of bits used per unit of playback time.
Video codecs will contain a sequence of frames, ie still pictures and, for compressed formats, movements between those pictures. Quality will vary depending on the number of frames per second, color space, resolution, etc.
Media storage formats will contain audio codec streams, video codec streams, captions, and meta information. It combine them to provide the audio or the video, with alternative or enhanced materials. In general a video will have one video codec stream, one or more alternative audio codec streams, and may have captions and meta information.