It's actually specific to combined cycle gas turbine plants where the waste heat from the GT is used to generate steam and eventually additional energy. This is opposed to simple cycle GTs where the mechanical output gas turbine is the only source of energy to the grid.
Sounds like the "big brother" of the condensing gas fired boiler you find being fitted in the UK these days.
Note the radial gauges have a tooltip to let you what they mean/represent. This was the one for CCGT: http://i.imgur.com/4kzFr2M
To extend - not gas as in petrol / gasoline but actual gas (natural gas, synthesis gas)