Remapping is reprogramming the ECU, the computer that controls most of your cars functions, to give the engine better performance by optimising settings that contol ignition, fuel and boost amongst other things. You will not believe how much better the engines run when this is done.
Do a search of the internet to check which of the bigger companies are available to you, Revo, APR, Superchips, MTM, Oettinger etc and see how you geton.