Gas turbine is a rota dynamic IC engine while Piston engine is a reciprocating IC engine. Working fluid (air+gas mixture) flows continuously through rota dynamic engine but doesn't flow continuously through reciprocating engine. In case of piston engine a batch of working fluid enters in to the working chamber, goes under various processes & finally leaves out the working chamber. Next batch of fluid then enters into the working chamber & goes through the same procedure. But in a gas turbine working fluid enters continuously while going under various processes leaving the chamber simultaneously.