Very simply, if the dependent variable is time series, it is most likely its present value depends on its past values (i.e. autocorrelated); then it is logically to include lagged values of this dependent variable as explanatory variables and this is the main idea of time series models.
Very simply, if the dependent variable is time series, it is most likely its present value depends on its past values (i.e. autocorrelated); then it is logically to include lagged values of this dependent variable as explanatory variables and this is the main idea of time series models.