Confer, commune, consult, advise, parley, treat, negotiate are synonyms when they are used intransitively and bear the meaning to carry on a conversation or discussion especially in order to reach a decision or settlement.
Confer implies comparison of views or opinions and, as a rule, equality in those participating in the discussion.
Commune, once a close synonym of confer, now is rare in this sense. In current use it usually implies spiritual intercourse (as in prayer or meditation or in a close union of minds and spirits).
Consult adds to confer the implication of seeking or taking counsel.
Advise often is not clearly distinguishable from consult except that it is more suitable for use regarding personal matters on which one seeks advice.
Parley, treat, and negotiate all imply conference for the sake of settling differences or of coming to an agreement on terms.
Parley stresses the talk involving the discussion of terms.
Treat adds to parley the implication either of a common will to adjust differences or of the need of diplomacy.
Negotiate implies compromise or bargaining.