Gas turbines are very similar to jet engines in design, except that they include extra blades -- called the power turbine -- on a shaft connected to a generator. It is relatively simple way to generate electricity with a minimum of equipment, but the efficiency of conversion is so low that it is seldom used except for times of intermittent use.
The gas turbine's biggest advantage is that it can be started and produce electricity significantly faster than a steam turbine. This rapid response makes it an attractive source for providing capacity during periods of peak electrical generating requirements. Gas turbines are also much smaller and less expensive than their steam turbine counterparts which makes them easier to transport and install on short notice.