Enry
Data sent to appliances, by whatever local/manufacturers name (such as Data2Cabs - yours, or Modas - mobile data system etc), is simply that. It is data (stuff with information in/on it) sent (by some means - usually radio transmission) to appliances (usually in their cabs, appliances being the red things that are often found in fire stations).
You say that I say such systems are being used throughout all brigades - here I BEG TO DIFFER. I said being rolled out. Which mobile data is. It is part of the Firelink project, which, as a serving fire and rescue service employee you should know all about, try reading FRS16.
Comments from fellow officers are right, there are some different systems presently in use, but they all share some common threads - they incorporate data interfaces (output devices such as monitors and printers, input devices such as keyboards, touch screens etc) transmission systems (radio normally) and the storage of data, sometimes only on a server for transmission, sometimes on the vehicle on a hard drive. There you have the basics.
In maybe even more basic terms - if (as is clear you do) you can use a computer and you have a connection to, that frighteningly technical bit of wizzardry, the internet then you have a similar system to mobile data. Input devices, output devices, data storage and access to data from outside sources. Simple really.
Now go on surprise us with your next question (on the subject of who should provide the data and whether it is free, or not, no doubt)?