Multimedia networking is defined as the network operation that have to do with video and audio.
Videos, basically sequence of images (array of pixels) is a type of content with high bit rate, from $100$ kb/s up to $3$ Mb/s. Videos however can take advantages of spatial redundancy and temporal redundancy (if several successive frames are similar, it’s not necessary to store them all).
Audios have lower bandwidth requirements and other differences compared to video. An analog audio is usually sampled at fixed rate. Each of the samples is quantized as a finite number on a finite interval, usually a power of 2. This process is the idea behind pulsed code modulation PCM (for example speech is encoded using $8000$ samples/s, with $8$ bits per sample, resulting into a $64$ kb/s). Popular compression standard for audio are MP3 and AAC.
All multimedia application tend to fall into one of these categories