Live refers to the manipulation and consumption of a subject in real time without significant delay, as opposed to playback after it has been recorded.
Live can be used to refer to audio, video, or both, that is consumed at the same time (or after a slight delay) that the original subject is being created. Examples of this are concerts, live broadcasts, and some streamed podcasts.
Live audio and video production usually has a much different set of requirements than does studio production of the same material. Gear used in live performances must be reliable, low impact, and usually durable, as to provide the least impediment to the performance as possible. Techniques often have a focus on minimize problems rather than providing the highest quality reproduction available.