I.) Parliamentary
Head of state is mainly ceremonial.
Chief executive can be forced out by "no confidence" vote.
Chief executive is chosen by the legislature.
Head of state has very long or life term of office.
The executive and legislative branches are jointly controlled by a ruling party or coalition.
II.) Presidential
Checks and balances hold between the executive and the legislative branches.
Chief executive is elected by the people.
Head of state is chief executive.
Effective communication is important because it helps to prevent and deal with conflicts. If one person wants something, and if they don't communicate it to the others, it might lead to a situation in which the others refuse then this without knowing, which would lead to conflicts.
So, in short: communication serves to prevent and lessen conflicts.
