It started, as far as I know, with the (slow) ethernet AUI or Attachment User Interface. Then it went through 100b(MII), to 1000b. The GBIC is a connector between an adapter, and the OSI physical layer. The virtue, is that you can have a plug on a switch that can service a gigabit token ring ethernet network, or a fiber ethernet network, or a twisted-pair copper one. The actual interface, is one that I don't recognize, I can say, that it's 20 pin, probably hot-swap, and probably an 8 bit wide serial connection.
As far as I know, the only two protocols that use the GBIC, are gigabit ethernet, and FC-AL.
There is now, the SFP, or Small Formfactor Pluggable, or mini GBIC. It is much smaller
the gbic interfaces with an mii, or media-independant tnterface, specifically a gigabit mii, which is an 8-bit wide serial interface. the reason this is a cool idea(tm), is that the layer 1 interface becomes abstract, so you can choose to use a rj-45, a SC duplex, or any other physical interface, all on the same device, so it's like legos, you can plug and play.
Commonly abbreviated as G-Bic, or GBic it is a small, matchbox sized silvery piece of metal that is used in many digital optical interfaces to allow for the operator to switch from Short-Wave to Long-Wave signaling standards(said operator would have two Gbics for each machine, one SW). A Gbic translates the serial formatted data it's fed into a transmit channel(the transmit channel goes down one cable, and the recieve signal comes up a second cable, similar to utp, except not twisted), and translates the incoming, and seperate optical data into recieved data. The Short wave gbics primarily use powerful LEDs to send data over low quality Multi-Mode Fiber cable over short distances. As I understand it, short-wave can be used with either MMF or Single-Mode Fiber transfering at distances up to 500 Meters, as I understand it. Long-wave Gbics use LASERs (no sharks involved unfortunately) over high quality Single-Mode fiber in distances to 2 Kilometers, or even 10.
You connect a Gbic to anything that can use fiber to transfer data, primary aplications include Tcp/IP, SONET, and SCSI. Hardware where these are used include optical networking equipment, including hubs, switches, routers, and network interface cards, and data storage; like SCSI host cards, and controller cards, resident in the reciever, and broadcaster respectively.
A GBIC connects to a media independent interface.