This is one of those times that it's hard to interpret the actual written text when I try to give you the syntax of a Stata command. What I am trying to get across with the [ ]'s is that that part of the command (the adjustment variables) is OPTIONAL. actually the by(stratavar) is also optional. Here are some examples that should make it clearer:
mhodds heartattack diabetes // heartattack is the outcome, diabetes the primary predictor
mhodds heartattack diabetes age male // same, except now adjusting for age and male
mhodds heartattack diabetes age male, by(htn) // same, except now ALSO stratifying by htn
You mentioned weights - I was not intending to do anything with weights here. But you're right that weights are one of the only times that Stata actually wants you to type in brackets [ ]. Don't worry about that yet though.