Inverse laplace transform of continuous transfer function

I am trying to get inverse laplace transform of continuous transfer function, I am getting following answer from MATLAB

-sum((4793*exp(r5*t) - 23510*r5*exp(r5*t) + 2644000*r5^2*exp(r5*t) + 660600*r5^3*exp(r5*t) + 67650*r5^4*exp(r5*t))/(500000*r5^4 + 36124*r5^3 + 11844000*r5^2 + 25260*r5 - 1600), r5 in RootOf(s5^5 + (9031*s5^4)/100000 + (987*s5^3)/25 + (1263*s5^2)/10000 - (2*s5)/125 + 1997/50000, s5))

What does r5 and s5 indicates in above equation?

Appreciate any help on this Many thanks :)