Gaviota generates and uses its own Endgame Tablebases (EGTBs) with its own format. It contains "distance to mate" information, which is how many moves are needed to mate the opponent, or to be mated.
There are two ways to obtain the Gaviota Tablebases. One is to generate them yourself, and the other is to download them directly from Josh Shriver site. The advantage of download them is that they already compressed and you will not have to do anything else. If you have a fast connection, it may be the way to go. Current files in that site are compressed with scheme 4 (*.gtb.cp4). Therefore, you may want to register the compression scheme in the ini file (see below).
Do it yourself... (Time and Space required)
The Gaviota Tablebases can be probed from your own program (engine or interface). The code needed to do this has been released under the liberal MIT license, so basically anybody can use it with almost no restrictions. The tablebase files themselves, compressed (*.gtb.cp?) and uncompressed (*.gtb) are also distributed under the MIT license. The latest release of the probing code (with the program example tbprobe) can be downloaded from the download page (look for TB probing code). Alternatively, it could be downloaded directly from the Git Hub Gaviota Tablebases repository.
Who is using the Gaviota Tablebases besides Gaviota?
Engines (probably not a complete list)