output of "REGRESSIONE" (italian version of excel) in the component "ANALISI DATI"

Where could I find a detailed explication of the ratios resulting from a REGRESSIONE Analisys?

i.e. which method/test is used to give a "p value" as a result of the application of REGRESSIONE to a couple of matrix? Ki-square? o t-student? or...?

Thank you