how does body language contributes to an effective conversation?

Body language adds emotions to a conversation and helps make an abstract idea comprehensible. Through facial expressions, hand gestures and body movements, the audience can easily perceive the true feelings the speaker has for the subject he is engaged in. For example, one can tell despise from frowning and agreement from a smile. When we try to explain something to others, body languages leaves a more vivid impression to the audience than words. We tend to open our arms to show that something is large instead of telling the exact dimensions for this purpose.