The F-Distribution Calculator computes the p-value associated with a given F-statistic and its corresponding numerator and denominator degrees of freedom. It is primarily used in hypothesis testing for comparing variances between two or more groups, such as in ANOVA or regression analysis. By selecting either a left-tailed or right-tailed test, users can determine how extreme their observed F-value is under the null hypothesis, helping to assess the statistical significance of model or group differences.