Guys Guys !!!!!!!!!!!! come on!!!!!!!
@ ibnekhalid asked a very simple question and pple have answered every thing but his query!!!
In the R type plugs "R" stands for Resistor type and thus this type of a plug provide around 5000 ohms of resistance.
These plugs are usually used in cars with a lot of electronic equipment to avoid intereference.
Usually all the new cars eg EFI Civic Vtis, Corollas etc) use these type of spark plugs as original equipment.
As far as improvement of performance is concerned it is a subjective question and I don't have information about that, but I think not much!
The easiest way will be to check your car's manual and if it says to use a resistor type S.plug then you can use them.
Now how will you know that your car recommends the R type plugs? Simple just read the Splug number in the manual. Following are the examples:
DENSO: K16-U11 (NOT Resistor type)
K16PR-U11 (Resistor type as you can see the R)
NGK: BKR5EY-11: Resistor type, because R has been used in the spark plug numbers.
NOTE: mind you these are not the fancy Iridium or Platinum or any other high end plugs just the regular plugs........so it has nothing to do with the fancy expensive spark plugs!
Hope this helps!