What is the language that is used for general social conversations and interactions called?

These 'social lubricant' words are called

phatic expressions or phaticisms.

They are intended to not convey information but simply mark a social need. Or rather the information is not based on reference to objects and actions but instead to conveying the social situation.

Of course it all depends on the situation. "How are you?" can be phatic, when the intention is to get the response "Fine. And you?", or it can be informative, when the intention is a description of one's hospital visit.

Informal works, or maybe colloquial. You might hear chit-chat, too, or small talk.

'Colloquial' is interesting because the noun form 'colloquy' refers to a formal discussion, the opposite of the adjective.

Vernacular is another word for it.

http://www.oxforddictionaries.com/us/definition/american_english/vernacular