Question

the practical aspects of communicating with others, or the social “niceties” of language, are referred to as

Answer 1

The practical aspects of communicating with others, or the social “niceties” of language, are referred to as pragmatics. 
Pragmatics deals with language in use and the contexts in which it is used. So, your use of language will change depending on the social situation or the people you are talking to.