In this picture, my eyebrows are down. This lets the "listener" know that I am asking a long response question. Without this facial expression, the "listener" might not know they are supposed to give an elaborate answer.
In this picture my eyebrows are up. It is called a WHQ facial expression because it requires questions that involve words such as Who, What, When, Where and How. This lets the reader know that I am asking a yes/no question. In some situations, if my eyebrows were not raised, it would give the "listener" the impression that I was simply making a comment.
The below picture means "try" in sign language. This sign uses a facial expression known as "tight lip". It is mainly used for signs that deal with conquering a task, overcoming a fear or working hard.
The next sign means "soft". The facial expression is often called "O Mouth". This expression is used when dealing with signs that mean light in weight or describing something that is soft in texture.
The next sign means "not yet". The facial expression is sometimes called the "hanging tongue" and it used to emphasize laziness.