What is this symbol? I've been seeing it on a lot of questions

K-1 (K to the power of -1) ?

I've seen it on Heat capacity questions, like this -
J mol-1 K-1 (I know J mol-1 = joules per mole)

I've looked everywhere and i just don't know what it is! I'm sure this is a dumb question...lol

Thanks

it means it is the reciprocal of K,i.e.,K^-1=1/K, for ex., meter second^-2 means (meter)/(second)^2

K^{-1} = 1/K

reciprocal

J (mol K)^{-1} looks like units for entropy per mol