Linguistics for LT : 3&4 round

I learned about the 5 features  of communication at the Linguistics for LT class. I try to paraphrase each feature.
1. Interactional function; Communication is a dialog not a monolog.
2. Transactional language; The language used to tell somebody a meaningful content.
3. Direct or Indirect; Direct means a message is clear, Indirect means it is unclear.
4. Metaphor or Idiomatic; each language has unique metaphors or idioms, but it is difficult for non-native speakers to acquire them. 
5. Displacement; Only human language enables human to  talk about places or people that are not in front of him or her.