Logistic regression is a statistical model used to predict binary outcomes like disease presence/absence from several explanatory variables. It is similar to linear regression but for binary rather than continuous outcomes. The document provides an example analysis using logistic regression to predict risk of HHV8 infection from sexual behaviors and infections like HIV. The analysis found HIV and HSV2 history were associated with higher odds of HHV8 after adjusting for other variables, while gonorrhea history was not a significant independent predictor.