  We review the assumptions and the logic underlying the derivation of DLCQ
Matrix models. In particular we try to clarify what remains valid at finite
$N$, the role of the non-renormalization theorems and higher order terms in the
supergravity expansion. The relation to Maldacena's conjecture is also
discussed. In particular the compactification of the Matrix model on $T_3$ is
compared to the $AdS_5\times S_5$ ${\cal N}=4$ super Yang-Mills duality, and
the different role of the branes in the two cases is pointed out.
