dlmat(objname , eig ) specifies an spmat object that contains the spatial-weighting matrix W to be used in the SAR term(SAR). eig forces the calculation of the eigenvalues of W, even if objname already contains them.
elmat(objname , eig ) specifies an spmat object that contains the spatial-weighting matrix M to be used in the spatial-error term(SEM). eig forces the calculation of the eigenvalues of M, even if objname already contains them.
The source of the explanation is from Maximum likelihood and generalized spatial two-stage least-squares estimators for a spatial-autoregressive model with spatial-autoregressive disturbances, D. M. Drukker, I. R. Prucha, and R. Raciborski.