If N is a ring (instead of a module), then the free module of rank 1 over it is used instead. If M or N is an ideal of ring, then the underlying module is used instead.
The source of this document is in /build/reproducible-path/macaulay2-1.25.05+ds/M2/Macaulay2/packages/Macaulay2Doc/functions/Tor-doc.m2:46:0.