Body language in communication is very important, as it often represents 90% of a message.
What we say sometimes is perceived more accurately when others can also understand the messages that we send with our bodies or by facial expressions. Sometimes, we are saying one thing, but appear to mean another thing by the way that we move our face or our body. For example, if we say, yes" while shaking our head "no," the body is more instructive than the words and others will not believe what we have said. When we cross our arms tightly while speaking, others may believe that our mind is closed on a certain subject. If we lift our eyebrows while speaking, or pull our ear, or put our finger under our eye or on the side of our nose, in some societies, we can understand that we should be suspicious or careful, no matter what is being said by others. Using the raised thumb along a road in some countries, such as America, means hitchhiking but in other countries it may be a verbal or sexual insult. If we show the sole of our shoe in some countries, it doesn't matter, but in other countries it may be seen as disrespectful. Some nonverbal communication can signify power, such as the clenched fist or raised arm, or it might be seen as a powerful sexual insult. The salute, done correctly, demonstrates respect for a flag, country, or military rank, but done in a sloppy way gives the opposite reactions.
When we are learning a foreign language, it is very important that we use appropriate body or facial language, which is acceptable in that culture or society. Otherwise, no matter how carefully we use the language, others will not believe that we are culturally sensitive. In my classroom in China, students are often speaking in good English, but laughing in Chinese, by hiding their mouths. Chinese laughter is very good when speaking Chinese, but in speaking English, one should also learn the facial or body customs of English speakers, which is a more open laughter. Then both the oral language and the body language will work well together. Each of us learning a foreign language needs to know not only the correct words to say, but also the right body or facial language to use.