Gear is a broad term which is used to incorporate any and all equipment used in audio or video production. This includes microphones, amplifiers, speakers, signal processing units, digital audio workstations, and plugins.
Note: Differences between similar pieces of gear and which piece of gear is best for a particular application are often hotly debated topics among professionals in the field of audio and video production, so there may not always exist a definite answer. Please keep this in mind when forming your questions.