What is the difference betwene simple linear regression and multiple regression?

Simple linear regression is performed between one independent variable and one dependent variable. Multiple regression is performed between more than one independent variable and one dependent variable. Multiple regression returns results for the combined influence of all IVs on the DV as well as the individual influence of each IV while controlling for the other IVs. It is therefore a far more accurate test than running separate simple regressions for each IV. Multiple regression should not be confused with multivariate regression, which is a much more complex procedure involving more than one DV.