How is it different from other forms of communication?

Dialogue is focused conversation, engaged in intentionally with the goal of increasing understanding, addressing problems, and questioning thoughts or actions. It engages the heart as well as the mind. It is different from ordinary, everyday conversation, in that dialogue has a focus and a purpose. Dialogue is different from debate, which offers two points of view with the goal of proving the legitimacy or correctness of one of the viewpoints over the other. Dialogue, unlike debate or even discussion, is as interested in the relationship(s) between the participants as it is in the topic or theme being explored. Ultimately, real dialogue presupposes an openness to modify deeply held convictions.

There are many definitions and types of dialogue, but a common denominator relates to a quality of conversation in which the whole becomes greater than the sum of its parts.

Dialogue can also be described succinctly as a quest to

...jointly create meaning and shared understanding through conversation. -- L A Franco
...in a dialogue, the important part is not the particular opinions--but rather the softening up, the opening up of the mind, and looking at all the opinions. -- David Bohm

In this process, unexpected shared experiences and areas of agreement can be identified and fresh understanding and innovative approaches to complex issues can emerge. These are not soft outcomes. They are the essential  underpinnings of better decisions and the development of broad stakeholder commitment to change. It depends on relations of trust, equality and respect and requires  a different sort of reflection based on self awareness and empathy.