In General, What Does "Degrees of Freedom" Refer To? Find $\mu$

Essay

In general, what does "degrees of freedom" refer to? Find the degrees of freedom for the given information, assuming that you want to construct a confidence interval estimate of $\mu$ : Six human skulls from around 4000 B.C. were measured, and the lengths have a mean of $94.2 \mathrm {~mm}$ and a standard deviation of $4.9 \mathrm {~mm}$