Sorry if I wasn't clear. I was saying that ceramic capacitors have the lowest inductance, especially surface mount types. SM ceramic types typically have inductance of the order of 0.5 to 1 nH while leaded film capacitors can have 10 to 20 nH. So, for the same value of capacitance, the resonant frequency of the film type is likely to be about 1/4 of that of the ceramic chip. Above the resonant frequency the effectiveness for decoupling reduces rapidly so as the frequencies you are dealing with increase you must reduce the value of the decoupling capacitor. Hence the common use of a small value ceramic capacitor in parallel with a larger electrolytic.
As for what "higher frequencies" means, it is all relative. For the work I used to do before retirement I used to consider frequencies over about 1 GHz as high as they need the use of different techniques.
Russell.